A/C or Heat Pump Fan Condenser Unit Fan diagnostic questions & answers - FAQs:
Questions & answers help diagnose problems with the air conditioner or heat pump condenser unit fan: fans that won't start running, won't stop running, hum, click, buzz, or run intermittently utlimately lead to loss of heating or cooling.
The condenser unit fan is a blower that moves outdoor air across the condensing coil found in the outdoor compressor/condenser unit. The movement of outdoor air across the condensing coil transfers heat to outdoor air and allows high pressure/high temperature refrigerant inside the condensing coil to condense from a gas back to a liquid refrigerant. This series article discusses the diagnosis and repair of problems with the outdoor compressor / condenser fan and fan motor, including fans that wont' run, fans that run at slow speed, and fans that won't stop running.
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Avoid confusion between the indoor blower fan and the outdoor condenser fan: the compressor / condenser fan is in the outdoor unit and is used to cool the outdoor condensing coil. If you are troubleshooting the indoor air handler that delivers cooled or heated air through the duct system and supply registers, see BLOWER FAN OPERATION & TESTING - home.
What is the purpose of the compressor fan and its fan blades? - Mike
Mike the reason you see a fan on the compressor/condenser unit comes from the need to transfer heat from the refrigerant system into outdoor air. Refrigerant gas is pumped from the indoor cooling coil through the outdoor compressor motor. The compressor produces high-temperature high pressure refrigerant gas.
That gas then flows into the outdoor condensing coil - it looks sort of like a car radiator with finned tubing. As the hot gas flows through the condensing coil, the outdoor FAN blows outdoor air across the hot condensing coil
That cools the gases inside the coil back to a liquid state and at the same time is transferring heat into the outdoor air.
The liquid state refrigerant can then return to the cooling/evaporator coil back indoors in the air handler where it is used to cool indoor air.
The "magic" of an air conditioner or heat pump is that by INCREASING the temperature of the refrigerant gas to a high level outdoors we are able to move heat INTO outdoor air even when the outdoor air is warmer than the indoors of the building.
(Mar 5, 2015) Tak said:
Outdoor fan keep running even if we have the system turn off by the thermostat
(Mar 7, 2015) Susan said:
I turned my heater off and kept hearing it running. It's a heat pump and everything was frosted over. I just pulled the outside ac breaker out. What could be the problem
(Sept 14, 2015) Brent said:
My unit is cooling fine but the compressor and outdoor fan does not shut off even when I turn the thermostat to off.
On some compressor / condenser units the fan may run before or after the compressor motor has shut off, but it should eventually stop. If it doesn't there is a control or wiring problem to be found and repaired.
In that case I suspect a wiring short or a control board or relay failiure at the compressor/condenser. I'd shut off the system and ask for service.
Brent a search of the InspectApedia website for "COMPRESSOR WON'T STOP RUNNING" finds
COMPRESSOR / CONDENSER DIAGNOSTICS at inspectapedia.com/aircond/HVAC_Condenser_Unit_Diagnosis.php
that includes a section titled HVAC COMPRESSOR WON'T STOP
where can i find a install video for a fasco 1/6HP FLP1.3 230V 1075RPM Center AC unit - Richard 10/16/11
Richard, Fasco provides replacement and OEM electric motors including for HVAC equipment. You can contact Fasco directly through their website at: fasco [dot] com - you'll find that the company will be glad to assist you with installation manuals, guides,
From TC: Instead of blowing air out of the top my fan is sucking air in from the top and blowing it out of the side of the outdoor unit. I have 3 units same brands and 2 of them are blowing and 1 is sucking. I did have to replace the capacitor but I marked the wirers and pput them back the same. is this a problem?
TC, models of compressor/condenser units vary in which surfaces of the unit are air intake and air exhaust. As long as you don't block the intake and exhaust you'll be ok. But looking at your condenser unit design, typically you will see that outdoor air is drawn through the condensing coil first and then exhausted by the fan - the fan is usually "pulling" air through the coil not pushing it in that direction.
However, your fan motor could be running backwards. See "How can I diagnose and repair a condensing unit fan that is running backwards" Q&A below.
From Brent K: I have a Samsung Ductless 3 split A/C unit. The other day I noticed the condenser fan running backwards at a slow speed.
At the compressor/condenser unit, air should enter the cooling fins and drive out through the fan. When the condenser unit was first turned on the fan ran clockwise - in the right direction. But when the high speed kicked in the fan motor came to a stop then started to reverse direction. When the low speed kicked back in the fan motor came to a complete stop until the high speed kicked back in then it started turning in reverse again.
The cooling ability inside the house also diminished [as it would be if the compressor/condenser is having trouble cooling the refrigerant back to a liquid].
Basic fan motor diagnostics: I checked out the fan motor windings with an ohms meter. They didn't match what was published in the service manuel but there was an acceptable resistance level similar to other fan motors I have come across.
The controller card [circuit board] checked out OK with 220V on the pin for low speed and when the condenser coils heated up the high speed kicked in and the high speed pin had 220V there. Good I thought the controller is working.
Next I looked at the run/start capacitor. The capacitor was a small black plastic block not one of those oval or round oil filled ones. I disconnected the leads after discharging the capacitor and checked it out with my multimeter set to capacitance. Sure enough the meter showed nil not the 4uf I was expecting. I called around to motor repair shops (HVAC shops sometimes give me a hard time and found a replacement 4uf 450VAC start/run capacitor for $11.00 CDN. Installed it and not the fan runs properly on low speed and high speed.
So my High School electrical training and 1 hour of diagnostic work saved me a bundle. If there had been a controller or refrigerant problem I would have called in a HVAC tech. - Brent K. 7/26/11
I have a nordyne model js3bd-030k that after been running for couple of hours the fan will suddenly stop even when you still feel the air circulating and out of the vents any body would know what is causing the fun to act this way any help will be greatly appreciated. thanks for any help
Mario, the air conditioner or heat pump diagnostics on this page apply to the outdoor fan found on the condensing unit. But as you are talking about stoppage of air coming out of your indoor supply registers, you will want to take a look at the diagnostic notes on the indoor air handler or blower fans (the indoor unit that circulates air in the building) - see BLOWER FAN OPERATION & TESTING.
I have an ongoing problem with my A/C unit. It is working until it gets very hot (over 100 degress here in Texas) and stop blow the cold air. I called a tech last year and he replaced the fan motor twice, once with a same model and next with a larger fan. Again this year I'm having the same problem. Any idea what could be teh soulation? - Abby
Abby I am having this problem and I can wait untill the late evening when the temp drops or the unit becomes shaded I can reset a swithch and it turns it back on and it will blow cool air untill the next day when it does the same again. I suspect it is the overheat switch because mine is always popped - Ernie
If a fan motor is replaced repeatedly I'd ask the service tech and service manager to do some further investigating as something else may be destroying the fan motor. Examples of other problems that can ruin the blower fan or condenser fan motor include:
- an improperly-sized start/run capacitor that fails to drop the start capacitor out of the circuit once the fan is running can burn up the fan motor start windings
- consistent abnormally low supply voltage
- a mechanical problem stressing the motor such as a blower assembly bearing or shaft problem or improper fan/blower connections or mounting
come home to find the home hot and the condenser fan not working and the compressor making a humming noise. Took outside condensing fan off and got it freed up, oiled the bearings and it works, but the compressor is still not coming on. Whats Next? Thanks for your help. - Johnny
my A/c will run for 1/2 an hour them the home circuit breaker switch trips. A/C units seems to run properly until the CB trips. I've repeated this over several days 6 times. - George
Johnny, it sounds as if the problem is not the fan unit but the compressor motor itself is not starting. See COMPRESSOR / CONDENSER REPAIR where our diagnostics of that unit begin. A humming A/C compressor is unable to start; either the motor is ruined or you might just need a start/run capacitor.
George: as with Johnny's case, if your compressor unit is tripping the circuit breaker it's drawing excessive current. The motor may be running and may seem ok but drawing high amps. You need help from a service tech who will check for those conditions, or take a look at the same link we just suggested to Johnny, above. It sounds like a component is overheating; usually a tripping CB means a bad compressor motor or a control or problem causing the compressor (or another component) to draw high current.
put hard start on and it running again thanks for all your help - Johnny
My compressor fan motor went bad. OEM was RPM 840/2SPD. The replacement was a 1075 RPM. Unit runs for about 30 minutes and shuts off. Could faster motor moving too many CFM be insufficiently cooling compressor and how?
OEM was RPM 840/2SPD looks like a two-speed fan motor; if you replaced it with a single speed unit, and IF the original wiring was using two speeds, the new fan would indeed be acting differently. But you are describing the condensing unit fan. More air providing more cooling at the condensing coil would be an improvement in system efficiency and I'm not aware of a case where it would be a cause of insufficient cooling.
Unless ... it's not wired properly; if the fan is not running when it should, the result would be lower system efficiency and even risks compressor damage.
Ran into a very strange situation with my 3 ton HVAC heat pump. Capacitor, 240V relay both good. Windings on compressor and fan seem to be reasonable (Fan run winding 32.2 ohms, start winding 94.4, overall 125.9 ohms). Compressor run winding 1.3, start is 3.5 overall is 4.2 (expected sum of 4.8 ohm???).
When thermostat off, condenser fan runs. None of the windings are shorted to ground. When breaker is turned on, condenser fan starts up a little slower than normal then proceeds to full speed. When thermostat turned to cool, condenser fan quits and compressor turns on.
Pull one leg of compressor off and fan does not operate with thermostat on “off” or “cool” position. 24 volt ac to relay working correctly. Unit is 15 years old. Have you ever heard of similar situation ? - J.Y.
I am sorry that I don't know an immediate fix to what you describe and no I haven't quite heard this sequence before. Some speculation and arm-waving might be of a little help though:
A condenser fan that won't stop running, won't start running, or acts weird, could also be due to a bad fan contactor switch - one that sticks on, off, or has burned contactors. And as we cited above, a fan motor that is overheating can be going off on thermal reset - those don't quite match your problem description however. But be sure that contactor switch is working ok and clean.
A slow condenser fan startup could be a bad start capacitor even though the one in place seems ok - it's cheap to try swapping in another cap, no? But you might want to look also for low voltage on the circuit. Shorts and lightning strikes and power surges can also sometimes cause symptoms like this (as can mis-wiring 240V or 3 phase circuits).
Regarding When thermostat turned to cool, condenser fan quits and compressor turns on. if you are seeing a big voltage drop ( is there hard starting compressor motor?) and if fan is fed off one leg of that circuit, I wonder if that might stop the fan. Does it ever re-start once the compressor gets going? Sometimes a motor will look good when tested "off" - with nothing spinning, but when parts move, a winding can open up or a connector fail.
My last arm-waving would be to wonder if the circuit board has been fouled-up.
Regarding: Pull one leg of compressor off and fan does not operate with thermostat on “off” or “cool” position. 24 volt ac to relay working correctly. - that makes sense if as often the case a 120V fan motor is being fed by one leg of the compressor 240V circuit.
I've posted this fan startup problem on the Compressor/Condenser Fan Diagnosis/Repair page - perhaps another reader will have some smarter troubleshooting advice for us. Keep me posted on what else you find - what we learn will help other readers.
Follow-Up from J.Y. - fan startup trouble traced to defrost circuit
Good morning, sir. Apparently this issue is caused from the defrost circuitry. It makes absolutely no sense to me at this point; however, when I take the black wire from the fan motor that goes to the relay (defrost circuitry, not the 240 volt relay) and put on L1 (120 Volt AC) the fan operates normally. This really has me confused because I see no way for L1 to ever get to the fan. L2 goes to one side of the normally closed relay (defrost). The only place that I can see L1 goes is to the compressor from the load side of the 240 volt relay.
Apparently when the defrost mode is on when heating in the winter, the condenser fan stops and compressor is running while the condenser is defrosting. While this makes sense, I was unaware of this. Once I found out that the condenser fan shuts off during the defrost mode (thanks to HVAC friend), I check the output and found L2 (which is what you would expect since L2 is on the other side of the relay from the black fan wire).
I am going to have to study the diagram further to understand how this works. Currently while I am happy to get the AC going, I am clueless to how L1 can ever get to the fan motor. Pulling the compressor wire also has an effect that I don't understand.
To help others if they ever see this:
if your condenser fan runs when the thermostat is off, and then stops once your turn the thermostat to cool, and the compressor starts, move the fan wire going to the defrost circuitry to L1 so you get 220V on the fan motor. IF the fan starts operating correctly, something in the defrost circuitry is bad - either sensor or board.
On some heat pumps that use a defrost cycle, during that period the compressor runs and the fan turns off (the idea is to warm up the compressor). That would be normal operation.
If it's a properly operating defrost cycle on a heat pump, the fan might remain off and the compressor on for about 10 minutes.
If the system is operating strangely (leaving the fan on forever, or never turning the fan on - and other fan operation problems like a bad motor, contactor, capacitor, wire, etc are ruled out) then I suspect a bad control board.
But I'm confused about putting 220V on the fan circuit. Isn't your fan motor a 120V unit?
A tech replaced the dual run capacator on the outside unit of my heat pump system. The fan would not spin and he needed help over the phone to get the unit running again. Could an improper installation of the dual run capacator cause frost and icing? Previous to his visit I never had a problem with frost or icing. - Mike 5/24/12
Mike, maybe in some way I don't fully understand. The fan on the outdoor comprressor/condenser cools the outdoor half of the system and thus permits condensing high pressure high temperature refrigerant back to a liquid form. One would think that if the refrigerant didn't condense back to a gas it would not be properly metered into the indoor cooling coil and I'd guess that the result would be reduced cooling, not more cooling or excessive cooling and icing at the coil.
Usually an iced evaporator coil (cooling coil) results from
How wolud i if the fan motor of the condenser bad. I checked running caps and its good fan blade are good. - Johnny 4/11/12
If with power off the fan motor does not spin easily the motor or fan bearings are seized; but a motor could spin but not start if an internal winding has shorted or has opened.
Check to see if voltage is present at the fan motor wires. If voltage is present and if none of these steps will turn the blower fan on, and if you are certain that the motor starting capacitor is good (see CAPACITORS for HARD STARTING MOTORS), then we suspect that the motor may be seized.
If the fan blades spin but wobble, or if you can move the fan shaft up and down or back and forth where it emerges from the fan motor, then the fan bearings may be bad, causing wobbling and even binding of the motor assembly.
If the fan spins freely, there is no loose fan motor shaft play, and no fan wobble, checking the capacitor or even swapping in a new one is one fo the first repairs a tech will try as it's so easy and cheap.
On some fan motors that don't use an automatic-reset internal thermal overload control, there may be a ELECTRIC MOTOR OVERLOAD RESET SWITCH that has tripped off.
See VOLTAGE MEASUREMENT EQUIPMENT for a description of tools used to detect the presence of live electrical wires & devices and for the measurement of actual volts or amps - a step that you'll need to take with the motor out of the unit for testing.
Blower Fan No Start / No Stop - describes weird blower behavior can also be diagnosed and fixed - this article provides a detailed list of things to check.
Condenser fan motor, new, all capacitors, new, Works fine cools house for 1/2 hour then new fan motor shuts off and compresses hums, wait 1/2 hour and it does it all over again. help - Mike Nichols 5/2/12
my unit outside will not come on but it does inside what can be wrong - Larry 5/21/12
Mike it sounds as if you are describing a bad compressor motor, especially if you are dead certain the start/run caps are OK. See COMPRESSOR / CONDENSER REPAIR where we list diagnostic articles.
Larry: same advice as for Mike. If you are sure the controls are calling for the equipment to run and voltage is present, start by checking the diagnostic articles in the order listed at LOST COOLING CAPACITY.
fan want run on aircndiction out side unit it just make a buzz sound - Joe Russell 5/23/12
Joe: could be a bad fan relay or start capacitor; Does the compressor try to start?
The blower will come on in the air handler in heat mode and in manual ,but not in auto ,what gives - Clyde 5/23/12
Clyde this page is about outdoor compressor-condenser units. Your question describes a problem with the indoor cooling coil and air handler assembly - at the "More Reading" links at the bottom of this article above click on BLOWER FAN OPERATION & TESTING to read about that component and its troubleshooting. Could be a thermostat or relay problem.
have a heat pump not blowing cool air. The condensor fan will run for about 1 minute then shut off and not start again for a few mins. Once it starts up the same thing every time. This unit says it should be at 300 psig for both high and low pressure but when i put the gauges on it im only getting 155 on both sides. what could be causing this.
I suspect that the unit has a low charge and is causing the fan to trip or the compressor may not be pumping, im not sure. all i know is that when my gauges are on it they do not change in pressure when i engage the contactor - Cox HVAC 5/26/12
Your system compressor is not continuing to run, nor is the fan. Check the start/run cap and the control board as well as the relay.
I just had a new fan motor installed....$569.98! Also is it standard procedure to have wires sticking up from the top,,,,? These were told to me to be so he could reverse the motor if need be? - Vicky Cummins 6/18/12
(Apr 28, 2015) Anonymous said:
I have a red and white wire coming into my house for the thermostat from the AC unit. in the furnace I have red, white, green and yellow. which wires should I connect the red and white wires from the air conditioner to?
No not in my opinion. It is a poor and dangerous practice to leave live electrical wires protruding out of any appliance - it's a shock and electrocution hazard. Perhaps the tech intended this as a temporary measure to be sure s/he could correct a wiring error. But electrical wires should not be left exposed.
I read all the above but I think I'm still confused. Last summer, I came home to hear my outdoor compressor unit making a high squeeling noise. I turned the AC off for the day and the noise never reappeared. Yesterday afternoon (temps in high 90's for several days)I lost air conditioning again. The outdoor compressor was making noise but the motor and fan were not running and it felt very hot to the touch.
I turned off the AC and left it off till this morning. When I turned it on, I then went outside to check compressor. Fan wasn't turning so I took a stick and manually turned the fan blades. It then started up and continued to run for about an hour until the fan stopped turning again. I again turned the AC off for about an hour then turned it back on and the same result, fan would run for about an hour then stop spinning. Here's an observation: when the unit is off, I can take a stick and spin the blades freely in either direction. If you can help me I would appreciate it. Thanks - Don 6/21/12
We have a separate article on diagnosing compressor noises. I found it by searching InspectApedia for "squealing compressor" - the article is titled "HVAC Noise Diagnosis & Cure: How to Evaluate Air Conditioner / Heat Pump Compressor, Air Handler, Ductwork Noises", and you can find it by clicking on NOISE AIR CONDITIONER / HEAT PUMP in the links listed at the "More Reading" links at the bottom of this article .
Quoting from that article: Squeals, normal A/C compressor: Normal air conditioner compressor squealing: Some compressors emit a high pitched noise during normal operation or just at startup. This noise should be brief and just at start-up, and will probably have always been present on the system if it's normal. More examples of compressor squealing diagnosis are in teh Q&A in that article.
Our AC isn't providing consistent cool air. At start up, we get cool air for about 15 minutes, and then just regular air. This problem started when the temperature hit the upper 90's.
I don't believe that the compressor fan is working properly as there doesn't seem to be any air blowing out of the unit. I'm considering checking the capacitor, however, I've not done this before and I want to make sure I know how to correctly discharge it first.
Any tips or questions you have would be appreciated! - Al 6/25/12
Al if your compressor fan is not running that is certainly a problem and the place to start. Check the diagnostic suggestions outlined in the article above.
I have a heat pump, Its been running fine in 100 degree weather. Just recently the fan motor began to overheat and go off on overload. I replaced the fan motor and am still having the same issue. When the new fan first started, I thought "yeah", but i began to smell a heater smell coming from the top of the condensing unit. I'm not sure if the crankcase heater is on or not. What could be causing this? - Ethel 6/25/12
I'm not sure, Ethel, but you've made some excellent guesses. A fan motor that has a bad start/run capacitor may have trouble starting and may overheat the motor, as well as the other ideas you suggested. And a motor not properly mounted, or with a bearing that is binding, can also overheat. I think a savvy tech might also check for abnormal voltage level if everything else checks out ok.
Also check that the fan bearings are not binding, causing the motor to overheat.
My compressor was running all morning outside temp was 114 around 3:30 my compressor stopped running at around 6:30 I installed my gauges the low side was 120 and my high side was 228 after a couple of minutes the compressor kicked on after 20 minutes the readings were 450 high side 78 low side my house began blowing cold air the unit is only 7 years old it's an American standard 3 ton do I have a freon problem or should I start testing start caps or what - Glenn in Las Vegas Nevada - 7/10/12
Glenn, also check for a bad refrigerant metering device; the compressor could have trouble starting against high head pressure; if leaving the system off until pressures equalizes fixes the "start" problem then I'd check or replace the start/run cap and then if problems persist, look for a bad or icing-up TEV. Incidentally I do NOT recommend just installing refrigeration test gauges right onto equipment without using a purge step in the same process, using the proper refrigerant gas; else you risk contaminating the system.
I have an erratic running fan on my outdoor unit, fan not running, so replace ( Dual Cap) now fan ran like new or not at all, but the compressor motor still comes on. I checked the Dual start cap, and it check out ok once, but would fail the same test later. So I replace the capacitor (exact - OEM) and the compressor motor still came on, but not the fan. However, (the strange part) while thinking what was next, I lightly tapped on the top of the circuit board, in the area of the Fan relay ,and there others side by side, ( not for any reason ) just pondering. Then the fan started up and ran like new.
However, when the unit shut down, and restarts the fan may run great or not. When it does not, I go outside and lightly tap the top of the circuit board in location of the fan relay, the fan starts full speed, and I have cool air. This would make a little sense if it were a (mechanical relay), but its solid-state- no contacts there???? Go figure, maybe I need to troubleshoot the entire concert board, however everything is plug and play now days, and it is very unlikely I could get a component if I where to find it. I know a bit verbose, but I feel it could be so many things, so any suggestions would be appreciated.
Thanks, Brian C Carter - 7/14/12
(Apr 25, 2015) Anonymous said:
compressor runs for 3 minutes and shuts off and re start again after 5 minutes
Brian you've done some excellent diagnostics. Your description suggests that either there is a loose wire or an actual loose component on the circuit board in the compressor/condenser unit. Not only is having to tap on it not a reasonable way to live with air conditioning, it could be dangerous, risking a shock. If you can't see and fix a loose wire or connection to the board or to other wires nearby, I'd consider replacing the circuit board. In the article above where we list types of compressor/condenser fan problems we include this topic.
(June 12, 2012) Donn said:My house A/C turns on OK. The outside fan will not rotate unless I stick a paint mixer stick between the vent holes and give the fan blades a shove. Then it cools fine. Is the fan worn out and has it become unable to start itself?
Donn: you describe a classic case of a bad start/run capacitor. See CAPACITORS for HARD STARTING MOTORS
I have an erratic running fan on my outdoor unit, fan not running, so replace ( Dual Cap) now fan ran like new or not at all, but the compressor motor still comes on. I checked the Dual start cap, and it check out ok once, but would fail the same test later. So I replace the capacitor (exact - OEM) and the compressor motor still came on, but not the fan.
However, (the strange part) while thinking what was next, I lightly tapped on the top of the circuit board, in the area of the Fan relay ,and there others side by side, ( not for any reason ) just pondering.
Then the fan started up and ran like new. However, when the unit shut down, and restarts the fan may run great or not. When it does not, I go outside and lightly tap the top of the circuit board in location of the fan relay, the fan starts full speed, and I have cool air.
This would make a little sense if it were a (mechanical relay), but its solid-state- no contacts there???? Go figure, maybe I need to troubleshoot the entire concert board, however everything is plug and play now days, and it is very unlikely I could get a component if I where to find it. I know a bit verbose, but I feel it could be so many things, so any suggestions would be appreciated.
Brian you've done some excellent diagnostics. Your description suggests that either there is a loose wire or an actual loose component on the circuit board in the compressor/condenser unit. Not only is having to tap on it not a reasonable way to live with air conditioning, it could be dangerous, risking a shock. If you can't see and fix a loose wire or connection to the board or to other wires nearby, I'd consider replacing the circuit board. In the article above where we list types of compressor/condenser fan problems we include this topic.
(July 15, 2012) Sean said:
After returning from vacation where we turned off the ac, (and water)when we turned the ac back on one of the two units, stopped putting out cold air. after going thru this awesome website, i may have found the problem.
The condenser fan outside does not come on, so i used a stick to make it run, and it did ! thought i fixed it. but the fan speed was slow compared to the other unit and the air coming out was not warm like the other unit - and then within a few minutes the fan turned off again.
The fan motor is a Emerson - Part # 37L7401 - if it has a reset switch then i will try to figure out how to get to it ( i am not very handy - not sure how to remove the cover to get to the fan) - do you know if this motor has a reset switch ? The other thing i learned from the website, is that the problem could be the capacitor, not sure how to replace that, but will cross that bridge if neccessary.
If you could please give your opinion on what is the most likely fix for this problem i would greatly appreciate it. thank you. Again this website is awesome !
Sean if the fan spins freely with power off but won't start and run on it's own the first thing most techs will do is swap in a new start/run capacitor. It's worth a try. If you're not familiar with electrical wiring, as it can be dangerous, even fatal, I'd hire a professional.
(Aug 2, 2012) Mike said:
I have an outside unit that the fan has decided to become intermittent and gets extremely hot within seconds of being turned on. Based on what I have read here I think the fan may be shot (even though its not a very old unit), I have a new fan on order and will be looking to replace it as soon as it comes in.
My question is... should the compressor also be coming on when the fan starts? Or, and I'm hoping this is the case, is the compressor waiting for the fan to become active before it will come on (a kind of fail safe)? I have a middle of the line gibson unit that is about 5 years old (and unfortunately not covered by warranty)
Mike, the control board circuit in your outside compressor/condenser unit along with contactor relays and start/run capacitors are what turn on the compressor and fan - usually at the same time, but I'm not sure how models may vary in startup sequence.
The fact that the fan motor gets very hot suggests a bad motor or perhaps a bad fan bearing that is binding. If the fan spins freely when power is off, and if there is no wobble or play in the fan motor shaft/bearings (up and down or side to side) then more likely it's the motor itself.
(Aug 5, 2012) Bill said:
My A/C was running fine this summer, then the July hot humid heat wave hit with regular temps in the 90s. One day my AC compressor started making rumbling noises, and frost started forming on the coils. As the frost melted it leak
One put in a new capacitator, it made no difference. So for 2 weeks I've lived with 88 degree living room. Today a storm came though Chicago and a cold front of 70 degrees. I tried the system and it's working again just like it should. Any ideas what's going on? As soon as the outside temp goes around 85 is when problems occur.
Bill, you might take a look at NOISE AIR CONDITIONER / HEAT PUMP on this page at Continue reading where you will find an INDEX to RELATED ARTICLES that includes a live link - and also or perhaps better, see
AIR HANDLER / BLOWER UNITS
since it sounds as if you are talking about frost formation on the cooling coil in your indoor air handler, not the outdoor compressor/condenser fan unit (the article on this page)
On this page at Continue reading where you will find an INDEX to RELATED ARTICLES you will see
FROST BUILD-UP on AIR CONDITIONER COILS
which is what you need to review.
Or just search InspectApedia for "Cooling Coil or Evaporator Coil Ice-up or Frost Over" and you'll end up in the same place.
(Aug 6, 2012) Gary said:
New condenser fan motor, cap. replace by A/C guy yesterday. Fan runs for 15 min and quits. Compressor keeps running and gets very loud. This happend right after the guys left.
Gary, certainly I'd call the A/C service company back immediately and ask for a return call - and I'd leave the system off until then, as loud compressor noises could spell serious trouble.
(Aug 10, 2012) MaryAnne said:
With the old capacitor, the fan will run without stopping every few minutes. With the new capacitor, the fan will run for about 15 minutes, then stop while the compressor and indoor unit's blower fan continues running. I remember a few things about ac diagnostics and repair. This has me stumped.
I can't guess from just the information in your question - nor even tell if the system is working improperly.
I guess if the air handler blower stops before the thermostat is satisfied then I agree something's wrong. Could be anywhere from thermostat wiring or sensor to control board to condensate overflow switch to geez. I'd start by swapping in a new start/run cap in case the replacement unit was bad.
I'd also consider that if your fan motor was having trouble before, the root cause could be the motor, wiring, control panel - continuing to fail and no longer being overcome by the capacitor - like a motor overheating and going off on thermal reset.
(Aug 16, 2012) Mark said:
I have a tennant in a basement apartment that sometimes shuts the blower motor off on a switch at the furnace, the condenser fan and compressor continues to run, but icing forms since we do not have flow through the A-coil. Is this damaging the AC system?
(Aug 25, 2012) Paul said:
My AC unit seems to turn ON fine but after running for a while the breaker in the house sometimes trips or the fan outside stops running and cause the A coil to freeze up. Any Ideas? Could this just be a fan going bad?
(Aug 25, 2012) Chris said:
Replace capacitor fan will not start light humming coming from what looks like another relay that has a spring in it not sure what it is called
(Aug 27, 2012) compressor kicking in and out said:
i have just replaced the fan and laced new cap with it, now the compressor kicks in and out but there is no cooling. also when the comp does kick in and out it dims power slightly. had the original cap checked and told ok. wondering if i should have bought new one or if there is a freon problem or bad comp now to.
(Aug 30, 2012) Brian said:
Replaced fan motor last year because not working. Turned out to be the capacitor. In putting things back together, my buddy didn't tighten the fan blades on well enough. They spun off the shaft and one got slightly bent. I didn't have time to fix it and let the thing run with vibration. Probably not a great idea.
A week ago, the vibrating had caused the fan blades to slip a bit more down the shaft and they hit the compressor with enough force to snap off one of the fan blades. The capacitor shorted out somehow when this happened. Now, new fan blades put in and tightened by me (won't trust my buddy with that anymore), and brand new capacitor.
Turned it all on and it worked beautifully. Then, 10 minutes later, the fan stopped. Inside blower working fine. It sounded like the compressor was still working (humming). It's in the 90s, so there shouldn't have been any reason for the fan to cut out. Ideas?
(Aug 31, 2012) Carson said:
After Hurricane Isaac when power was finally back on, tried to turn on AC. Inside fan and outside compressor started but outside fan did not come on. Turned off unit and started doing dome research. Found this forum and did a little reading.
Saw that it could be a number of things. Went and turned the unit back on and the outside fan came on. I thought great until I went outside to check on it 5 minutes later. The fan was not turning but the compressor was running. I ran back inside and turned the AC back off.
About 30 minutes later I tried the AC again. The outside fan would run for 3 to 5 minutes and would stop. Any ideas what could be wrong? Is it the fan motor over heating or could it be the capacitor?
(Sept 24, 2012) Cheryl said:
I had the run cap replaced on my outside unit 2 months ago because the unit stopped working. Now, it has stopped again and the fan on the unit is not turning. What might be the cause, and how much should I look to pay to have the problem fixed?
Cheryl, see Roberts comments at the start of this FAQs section.
(Nov 11, 2012) Condenser/Compresser Unit said:
I have had my A/C off for about a month, it started to get cold so I turned on the heat, but I can I hear condenser outside turn on, 20 seconds later it shuts off. Then repeats till I jus et shut it off. The unit is just a yr and 2 months old. So hard to believe it's bad already. Any help Would be greatly appreciated.
(Nov 18, 2012) angel said:
I had a problem with my Condenser unit FROST BUILD-UP , (heat pump), thermosthat calling for heat.
Any help Would be greatly appreciated
ice on the outdoor coil when the heat pump is in heating mode may mean Lowes refrigerant a faulty refrigerant metering valve 830 you're blocked Coral or a fan that is not elaborating or something else that we didn't think of
(Nov 27, 2012) Rob Munn said:
The temp outside today is 0, and though I hear the fan in the furnace running, and air is coming out of the registers but there is no heat. I check on the heat pump and there is ice all around the base (from concrete onto bottom of pump). Perhaps the fan blade is frozen?
Should I pour hot water on it? Does it, as you have stated in one of your responses, have a defrost cycle and I should check in a quarter hour if it is running again?
At such low outside temperature I'd expect your heat pump system to have switched to backup heat mode. Is your backup heat not working?
My 4 ton Bryant unit does both AC and heating.
One of the two side by side breakers indoor often trips - I think the tripped one controls the outdoor unit because the fan for indoor air circulating still runs. I reset the tripped breaker, and it goes for another day or two, then trips again. What kind of problem is that?
Breaker trips in response to an overcurrent. A shorting wire, relay, or control can cause the problem, but more common is a failing compressor motor that is hard starting, thus drawing high current a startup. Ask for help from a service tech. S/he might try a hard start capacitor kit to see if that buys some time.
(Jan 6, 2013) Rob said:
hey ppl. you are all way more qualified than myself... im trying tp repair a small mini bar fridge for my girlfriend... im.usually quite good at fixing things but when it comes to cuircuit boards im lost... i opened the thing up and found that one of the twp green cuircuit boards makes a clicking noise (like an electric fence box, but only faster)...
. im looking at all these small capasotors and little resistors and can figure out what the hell to do...
can anybof you plz give me some advice.... i dont wanna go to an electrician... i wanna try fix this at home and learn something...
obviously need some advice tho... and you ppl seem to know what your talking about. any advice would be greatly appreciated. thanks. Rob
(Jan 13, 2013) Ruccardo said:
My fan coil starts only when thermostat on heat but fan does not start when in cool. External unit fan and comoressor starts regularily.
It can not be the capacitor neither the fan since it starts when heat. What can be the problem? The fan unit is Carrier model Fa4Nc048. Thank you
(Jan 13, 2013) Ernie said:
The fan on the outside compressor unit for the heat mode seems to be coming on late as steam comes from it for quite a long time before the fan comes on.
Is this normal or is there a control circuit adjustment for this.
(Jan 14, 2013) NATHAN said:
MY OUTSIDE FAN MAKING VERY LOUD NOISE AND IS BEARLY TURNING
(Feb 17, 2014) Kathy said:
my fan outside broke loose and is just hanging there with a bent blade...the unit shut off
That sounds right - you want it to stop; I would turn power off and leave it off until the fan assembly can be replaced.
(Feb 19, 2014) Dre said:
Outside condenser fan stopped. Replaced capacitor and fan motor it ran fine for about 2-3 days stopped working again ?
Dre I can't make a very useful guess with so little information, but in the article list above you might want to check out these diagnostic discussions:
HARD STARTING COMPRESSOR MOTORS
and CAPACITORS for HARD STARTING MOTORS
(Mar 2, 2014) Bill said:
What would cause the fan blades to actually rip of their mount two ripped off and the unit was vibrating a lot. It has done some damage on the inside walls will this have to be replaced too.
A loose fan mount or a bad fan bearing could do what you describe.
Also check the voltage level
(May 5, 2014) ernest said:
Condenser fan motor makes noise when the blade is on the motor and no noise when the is off the shaft
If you are removing the fan blades to find that the motor becomes "silent" three possibilities occur:
1. the fan blade is hitting something, maybe wobbling, or out of balance or bent
2. the motor bearing or shaft is worn but with the absence of load of the fan blade assembly the noise doesn't show up
3. there is another explanation we've not thought-of like a loose mount that only vibrates when there's the added weight of an out-of-balance fan blade, or something else.
(May 7, 2014) Sergio said:
Can freon shortage cause fan motor to wind up slow when first turned on? Just replaced the capacitor also.
Sergio, maybe in some obscure way I don't know about, but in general, no. The freon charge won't change the speed of a fan motor. As you already replaced the start capacitor, Look for a bad motor, bearing, low voltage, or a defective control.
(May 23, 2014) Mathews said:
Recently i have changed the condensing Coil of the Outdoor Unit. But when i switch On the A/C compressor works for a minute then stop working for 4-5 minutes then again start working for a minute then stops againthis cycle goes on. Can i know whats the problem ?
I'm unsure. Perhaps a bad control or an overheating motor.
(May 24, 2014) Jim Turner said:
outside unit-carrier- runs constantly. Air handler cycles ok. house is staying cool. What controls the cycling of the outside unit? Is there a relay somewhere?
Jim, in a normally-working A/C system the cooling equipment will run until the thermostat is satisfied. So if the building is gaining heat faster than the cooling system will remove it the system will keep running. The thermostat acts as an on-switch. Relays in the compressor/condenser turn it on in response to the thermostat.
(June 3, 2014) keith said:
My thermo is set on cool and 76 degrees in auto mode.usually my compressor kicks ..fan spinning etc..this time just coolair is being blown..no compressor.
In the links above see BURNED OUT COMPRESSOR and HARD STARTING COMPRESSOR.
Could also be a bad relay or control.
(June 6, 2014) Robert said:
My outdoor fan starts but after 20? minutes fan shuts off and indoor unit continues until I shut it off at thermostat. It's a 5 ton amana model vca60c2a . If I let it sit for a while and restart at the thermostat it will repeat.I live in s.la.
It's very warm so I'm trying to remedy this ASAP.i did some research and thought it could be a capacitor but the stick test will not restart the fan after it stops? Any help would be greatly appreciated!
(this comment is not published until approved)
That sounds like a control or relay failure. A capacitor is typically used to start or keep a motor running - a separate function.
(June 16, 2014) Nick said:
Wire of my AC outside the house has been knicked by the fan. AC does not work. How to repair the damage. Thanks.
If the wire didn't short out (which would damage equipment or trip a breaker) it can be spliced & waterproof-taped, or replaced completely.
WATCH OUT: for fatal shock hazards. Don't try working on live equipment. Hire a trained professional if you are not qualified to make this repair.
(June 19, 2014) nora said:
my air-conditioner is not cooling. I cleaned all the outside fins sprayed with water. The unit is not cooling. Also the unit is making an occasional buzzing noise. Not sure if I should call for repair? The problem is work and they charge so much extra to come after hours or weekend.
Unfortunately this problem is not likely to be one a homeowner without the training and equipment and supplies can repair.
(July 21, 2014) Brad said:
4 year old Payne heat pump will come on, run 20 minutes, begin cycling off & on, then will eventually stop - the fan and compressor stop. If I shut off the breaker, wait 10 minutes, it will click, then come back on if the breaker is turned back on only to repeat the process again. Tech has replaced the contactor and the start capacitor with no results.
Check for a freezing expansion valve
(Aug 5, 2014) Benster sebastian said:
my ac heatpump not working, indoor unit running normally with the thermostat and blower,but the condenser unit was not working, when i manually push in the contactor switch the compressor turn on but not the fan motor
Possibly a bad start / run capacitor
or a bad control board or relay
(Aug 17, 2014) Mike said:
My condenser fan won't start unless I manually spin the fan but, it only runs slow.
Mike look for a bad start capacitor
(Aug 30, 2014) Anonymous said:
I was told there are two capacitors in my air condition unit but I can only locate the dual capacitor...where would the other one be
(Bob) please see
(Sept 1, 2014) john said:
have a Coleman heat pump that is about 9 years old. having problems with the contactor not resetting, unit runs fine but kicks off after a short time.
try to reset contactor but it won't hold.seems to after it sits for awhile cooling down or something. can it be just a bad contactor? if I try and rest it wants to fire up but the contactor won't hold?? thanks
I'd try replacing the contactor relay
(Sept 10, 2014) Brandon said:
The initial problem was that the compressor would run but the condenser fan would not start.
The blades would/do turn freely when manually pushed. Tech came and replaced start/run capacitor today. The fan did run while tech was here. Now its a few hours later and the compressor is still running as expected, but the condenser fan has once again stopped working again. I can still easily turn the blades manually. Any ideas?
I'm not sure what wiring and controls the tech checked, but it would certainly be appropriate to give a polite call to the HVAC repair company's service manager to ask for a proper and complete repair.
(Sept 12, 2014) bob said:
replaced fan motor on a goodman ac unit the new motor will run about twenty minutes then get hot and stop running.
check for proper voltage
check for a binding fan bearing
check for a mis-mounted or misaligned motor
check for proper start/run capacitors
(Sept 17, 2014) Anonymous said:
I have a 220V condenser fan motor that is running 1/2 speed backwards when the AC is off. When AC turns on the motor changes direction (runs forward) but still only at 1/2 speed. I have replaced the contactor and dual start capacitor and that did not have any impact on the symptoms.
(Oct 6, 2014) Diane Feltner said:
Post another comment
(within the last minute) Diane said:
I hope someone can help me fix my goodman 3 ton heat and air unit heat pump.
The trouble I'm having is I heard this clicking noise like the fan trying to come on, but never did until
I took a stick and pushed the blades and they started moving than I went inside the house and the air coming out was not cool could anyone tell me where to start checking, I,m going to try to fix this myself .
The problem could be a bad fan start relay or (probably) fan motor capacitor or quite possibly something else - I can't tell much from your note.
Frankly you'd be safer hiring a trained HVAC repairman. Someone with experience can not only hone in quickly on the trouble but they're more likely to have test tools, gauges, refrigerant, and parts needed.
(Oct 29, 2014) clifford said:
I replaced my 2 ton payne unit condenser fan motor, and cap.and control contactor.but fan motor still overheats and cuts off it is a straight cool basic unit.what else could it be
If a fan motor continues to overheat I would check for
- a tight, failing or askew fan bearing
- low voltage
(Nov 6, 2014) Al said:
Outdoor fan works but no air coming thru the ducts inside.
Al the outdoor fan is part of the compressor-condenser unit, is used to cool refrigerant, and won't have to do with movement of air through the HVAC ducts in the building interior.
You want to find the air handler unit or blower assembly indoors - that moves indoor air through return ducts, past the cooling coil, and into supply ducts that deliver air into various rooms indoors.
(Feb 24, 2015) roosevelt said:
i have a heat pump system.while my heating system is working i heard a clicking noise from the outside unit.i see that the fan is not turning,but still have heat with the inside unit(furnace).can u help please
Sounds as if the compressor condenser is not starting and you're hearing a relay switch. If you still have heat indoors I imagine that's because your backup heat system is running. it's time to call for service; as your backup heat is working it's not an emergency but it would be smart to turn off the outdoor unit to avoid further damage.
(Feb 26, 2015) Anonymous said:
I have a Goodman A/C Heat pump unit. It's 30 degrees outside and I'm running the heat. I noticed that the outside air compressor unit was humming and the fan was not turning. I screwed around with it (shut the system down, turned the air conditioner on and off and then turned the heat back on) and now it's working. Is there possibly something wrong? Thanks.
Yes something is wrong. It sounds as if the compressor motor or fan motor is unable to start. Turn the system off until it can be repaired.
(July 19, 2015) c. de said:
Compressor will start and run fine for several days, then shut off and need to be cooled down with a hose, then runs again. 3 technicians have been out . one said not enough "Freon" and thermostat...that didn't work, the 2nd had to take 3 lbs of Freon out of unit that first one put in,
2nd one put in a new starter switch, worked for a while, then same problem, checked compressor didn't detect any issues, 3rd one checked compressor, said no issues. still doing same thing. house will cool fine for a while, then compressor shuts off and only fan runs and room temp. begins to rise...
compressor not working, if shut off breakers and run hose on compressor will run again? unit installed in 2004, do I need a new one. no one wants to work on it, because they say it would cost more than a new unit? Does anyone really know how to repair a unit, or do they just want you to buy new?
Low freon won't cause what you describe; more likey the compressor motor is failing.
(Aug 22, 2015) Tracy said:
The outside unit (fan and compressor) will not come on consistently.
It will run most of the day and then it won't start again for several hours, mostly at night. When it does run it works great and cools as it should with no unusual noises. When it doesn't start (meaning neither the fan nor the compressor will come on) it makes no noises whatsoever - not even humming. I have replaced the capacitor and the thermostat. Could it be the contactor?
- a loose wire or bad relay or control board that might be responding to temperature changes or vibration.
Also your tech may want to check for abnormally high head pressures in the system. A compressor can have trouble starting against high pressure on the high side.
(Oct 11, 2015) Sean said:
Thanks for info. My unit is having trouble in heat cycle. The compressor will hum, but fan doesn't turn and aux heat is provided. If I turn the breaker at the main panel off and then in, the unit will start just fine for several days.
We have charged he unit as it was low at one point.
Replaced the main panel breaker.
Replaced the starter capacitor.
Thinking must be compressor at this point.
Yes, a humming compressor is motor having trouble starting. Search InspectApedia.com for CAPACITORS for HARD STARTING MOTORS that might let you eke out a little longer compressor life.
(Nov 10, 2015) Cc said:
does the compressor outside your home supposed to run when you turn the heat on
Yes, if it is a heat pump and if the outdoor temperature is not too low.
Not If your compressor condenser unit is only supporting air conditioning.
Not if the outdoor temperature is so low that your heat pump cannot operate. Then you will be on back up heat.
(May 4, 2016) dave said:
compressor was not comming on, replaced with new one, it is doing the same thing not starting, 240v, new cap an contactor, Goodman heat pump
Well happily the installer will surely cover diagnosis and repair of this situation as you just paid for a new compressor. Check power, voltage, start relay.
Continue reading at COMPRESSOR / CONDENSER DIAGNOSTICS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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