This Air Conditioning Troubleshooting & Diagnosis FAQ (list of frequently asked questions about air conditioners) lists the major areas of investigation to be followed in diagnosing all types of problems with air conditioning systems and heat pump equipment.
Typical air conditioner concerns include compressor or blower assembly noises, failure of air conditioners to start or to keep running, inadequate cool air flow or air quantity, loss of air conditioner cooling capacity, reduced air conditioning output temperatures, loss of cool air supply, or even loss of air flow entirely.
Also discussed are various electrical wiring, fusing, overcurrent, and thermostat or control defects on air conditioners.
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Since the failure of an air conditioner to turn on, loss of air conditioner cooling capacity, reduced air conditioning output temperatures, loss of cool air supply, or even loss of air flow entirely can be due to a variety of problems with one or more components of an air conditioner or air conditioning system, after reviewing the lost air conditioner cooling diagnosis procedures described in this article, be sure to also review the diagnostic procedures at each of the individual air conditioning diagnosis and repair major topics listed just below.
To return to our air conditioning and refrigeration home page go to AIR CONDITIONING & HEAT PUMP SYSTEMS.
These questions & answers about diagnosing trouble with air conditioners and head pumps were originally posted at AIR CONDITIONING & HEAT PUMP SYSTEMS
Also see this series of A/C & Heat Pump Diagnostic FAQs sorted by major topic area are given at AIR CONDITIONING & HEAT PUMP SYSTEM FAQs LIST
On 2017-07-31 (mod) said: trapped ducts? fire hazard?
I don't understand the situation, Karl. If by "trapped duct" you mean ductwork is crimped that's repairable. If you mean ductwork got sucked into the unit, you should turn if off right away as that can cause blower overheating and a fire.
On 2017-07-31 by Karl
Hi. I recently bought a 1400 btu fral portable air con unit. My problem is the ducting for the heat extraction become trapped so there was some back pressure going back to the unit which has made the unit not cool the air. Everything else works apart the the air cooling bit. The unit is brand new. Is this a simple repair or is the unit broke entirely. Thanks for any help
On 2017-07-21 by (mod) concerns with torn damaged insulation anywhere inside of the air handler
Yes there are some possible concerns with torn damaged insulation anywhere inside of the air handler, including
1. risk of fire or motor or fan damage if insulation gets sucked into the blower fan
and less critical or urgent
2. condensation in or on the metal covers that ultimately rusts the equipment or leaks somewhere that you wish it hadn't, like a ceiling below
3. if much insulation is lost, possibly un-wanted heat-gain into the blower compartment, increasing system operating cost during cooling season or vice versa, heat loss and higher heating costs during heating season
At DIRTY COOLING COIL / EVAPORATOR COIL - http://inspectapedia.com/aircond/Clogged_Evaporator_Coil.php we describe a blocked coolign coil and several problems that occur if insulation falls onto the cooling coil surfaces - on your system that might not be in the same area as the damage you describe.
I wouldn't sweat a trivial nick or an inch of disturbed material but if the insulation is missing entirely over parts of the blower compartment or is loose enough to get drawn in I'd have it replaced.
On 2017-07-21 by Doris
The insulation in the lid of the blowe motor side is torn and damaged, does it make a difference?
On 2017-06-09 by (mod) fan won't run, bad capacitor
If you mean the fan doesn't run unless you give it a push, that is probably a bad start/run capacitor for the motor
On 2017-06-09 by Carrier
Need help on way carrier a.c. unit relay is not spawning unless I give it a push
On 2017-04-10 by ray
reem 2 ton ac cools coil but blomer no blow
On 2017-02-16 by Mike
Hi I have problem In my split Aircon unit when I turn it on the compressor and the condenser fan is working after 20sec. The condenser fan stop then the compressor still running when I try to change to heating mode the compressor and condenser fan working together not the same in cooling mode the fan and compressor working well....Do you think what is the possible trouble during cooling mode? Tnx the unit is also York/Johnson control
On 2016-08-09 by (mod)
If you don't have the user's manual for your air conditioner you can find one at http://inspectapedia.com/heat/HVAC_Manuals_Air_Conditioners_Boilers_Furnaces.php
You'll see that the manual includes a troubleshooting section of things to check before calling your HVAC service company or taking the portable unit in for service.
Here are some things to check, more or less in this order.
Check for a dirty or blocked air filter and clean or replace it as needed. Restricted airflow can cause the unit to cycle on and off rapidly.
Check the fan speed settings. If the fan speed is set low, set it to its highest speed. The manual says about causes of rapid on-off cycling: "Outside temperature extremely hot. Set FAN speed to a Higher setting to bring air past cooling coils more frequently."
On 2016-08-09 by Tommy
My portable air conditioner a Comfort Air turns on Cycles blows cold several minutes Cycles down fan only after a period of time it Cycles on again a few minutes and then goes back to fan. What might be the culprit be?
On 2016-08-08 by (mod) Error codes depend on the brand and model of equipment; E1 error code may mean a dirty air filter
Error codes depend on the brand and model of equipment; if you don't have an owners/installation manual that's what we need to diagnose the code.
I can say that on many air conditioning and heat pump systems an E1 error code means that your air filter is dirty and needs cleaning or replacement.
On 2016-08-08 by Anonymous Error E1
On 2016-05-30 2 by (mod) very loud crackling sound
Sam you need an onsite expert; the sound could be a control, relay, or even sheet metal movement. I just can't say.
If your system has an electrostatic air cleaner installed, that may be a normal noise of the unit zapping dust.
On 2016-05-28 by Sam
Need Help with AC Sound. I have a 1.5 ton Split AC. Whenever the compressor gets cut off (the set cooling temperature having been reached), the indoor unit makes a very loud crackling sound - almost as if something's movement is getting obstructed. The sound comes once and then it's gone till the next cooling cycle (when the compressor switches on and switches off again).
Need urgent advice please. What could it be? Can I repair it at home? There's no problem with cooling or fan speed per se.
Thanks in advance,
On 2016-04-21 by (mod) lost refrigerant or perhaps a control failure
Either the system has lost refrigerant or perhaps a control to switch from heating mode to cooling mode has failed.
On 2016-04-21 by James Trane Heat Pump
2013 Trane Heat Pump worked great cooling the house before winter,turn it on now and call for cool and real hot air blows out the vents not cool,why?
On 2015-12-26 by (mod) Tempstar 2.5 ton gas pack comes on, but the condenser fan will not
see FAN, COMPRESSOR / CONDENSER UNIT
On 2015-12-25 by John M
my compressor on my tempstar 2.5 ton gas pack comes on, but the condenser fan will not. unit not putting out cold air.
(Jan 15, 2013) Mike said:
When the thermostat clicks on the heater doesn't always come on, the outside unit is running but the inside unit has a humming sound. This is a Carrier heat pump,does it have something to do with the air handler and what can I do?
This question was posted originally at HEATING SYSTEMS
Look for an obstruction blocking a moving part like the blower fan
Look for a frozen fan motor, try a hard start capacitor or replace the motor if that's the problem
See HVAC NOISE group 3 - hiss, huff, hum where we discuss humming sounds coming from the compressor/condenser unit.
5/08/14 Laurie said:
I have a Heil model number PH5036AKB4 ac/heat unit my problem is that it will run fine on heat no problems at all but on air it will blow cool air for about 30 mins if I'm lucky and then it just stops blowing and then u have to cut it off and wait for it to want to work again which can take any where from a few hours to two or three days please help it's so hot and I have asthma what can I do to fix it Thanks so much
Laurie, I agree that you need an on-site visit from a trained HVAC tech. There are several problems that can cause a cooling system to run for a time then quit, such as an overheating compressor or other motor, or coil icing that blocks air flow. Something like a low refrigerant charge (find and fix the leak) or a defective refrigerant metering device could be at fault.
my a/c united just stop working and nothing will come on
non, start by checking the fuse or circuit breaker;
(Feb 13, 2014) Mike In Warner Robins,GA, email: firstname.lastname@example.org said:
I have a Rudd Heat Pump A/C Unit. Notice yesterday when I set the room thermostat to about 78 degrees a blue Aux Heat lite comes on. The unit runs about 15 minutes and the C/B trips. If I keep it below 78 degrees and the lite does not comes on, the unit will continually run (blowing only warm/cool air). I also notice yesterday that my outside unit fan blades iced up (shut the power off from the unit).
This morning I got out and knock the ice off and restarted unit. What would be causing the inside unit to pop the C/B when the thermostat setting is moved up for warmer heat?
Mike, sorry that you're probably cold; Though setting a room temp up to 78 is a bit challenging.
Most likely you've already figured out that the problem is with your backup heat system - which kicks in when the heat pump can't extract enough heat from the outdoor air. Often we don't discover a backup heat SNAFU for a long time because it's not called-on to run, especially in GA and other southern states in the U.S.
Search InspectApedia for
Heat Pump Backup Heat
and you'll see our diagnostic articles for that topic.
(Feb 14, 2014) Susan said:
During the summer, our AC stopped working. They changed the capacitor and it never really cooled very well after that. It does not seem to be blowing very well. The same unit heats our home. It is not a split unit. When the axillary heat comes on, the house gets warm, but at a cost! We have checked most of the duct work, but some of it is not visible. It is a mobile home . It worked fine until all at once it stopped. Any idea?
Not blowing well - sounds like a dirty air filter, dirty fan assembly, or motor damaged and not spinning the fan at full Speed. E.g. A loose fan belt.
(Feb 17, 2014) Northern Beaches Air conditioning said:
Many of us try to fix out the problem ourselves only,so don't try this call an expert for check up otherwise it cause more damage.
I agree with the A.C. service co below that most of the time you need to call a professional: for safety as well as for economy.
However it can be helpful to understand a few basics that homeowners should be checking themselves such as
- a dirty air filter
- obvious SNAFUs such as loose, damaged, disconnected ductwork
- condensate handling SNAFUS such as leaks
You'll still need a professional to repair some of these problems but for most able bodied people there's no sense in calling a professional to do a homeowner chore like changing an air filter. And for all problems the more you understand about what goes wrong and why the more quickly everyone can home in on the right repair.
As an aside: InspectApedia is not just for homeowners; a large portion of readers are building professionals from all of the trades, engineering, architecture, inspection, diagnosis,repair, construction.
(Feb 21, 2014) Gary said:
I have a heat pump with a gas furnace as my Aux heat. Air handler is 17 years old with a Honeywell digital thermostat. Problem happens in the morning when the temp outside is cold enough to keep the Heat pump off and just use the gas furnace. Thermostat is set at 67 deg at night then called to heat to 70 in the AM it will start normally but only raise temp 1 degree then air handler and furnace shuts off.
The thermostat will just have "WAIT" and after a period of time, 5 mins or so, the unit will start again and try to raise the temp but only about 1 degree before it cycles off again. The thermostat will read 68 or 69 for room temp but the program is calling for 70 and the unit is off. Why do I have this delay? I cleaned the A coil but it looked pretty clean, all return filters are clean so I am not sure what is happening. Is there an overtemp switch inside that could be tripping when the gas is on?
Thanks for any help
I don't know,Gary, but often when weather switches a heat pump over to backup heat we find operating defects in the backup system that were there for a long time but never evident because the backup wasn't in use.
Since your backup heat is a gas fired furnace it's being controlled by
- a circuit board in the heat pump that switches over to backup mode
- normal gas furnace controls including a limit switch on the furnace
Try watching the limit switch to see what it's doing. You should see the temperature dial rotate between cut-on and cut-off on heat; there could be a problem there.
let me know what you see
what is the EM HT SWITCH FOR?
Ann, no wonnder you're asking - it sounds as if someone didn't realize that EM HT would not be obvious to everyone. I'm guessing it means "Emergency Heat"
(Mar 28, 2014) Anonymous said:
I have a carrier programmable thermostat....If I push the mode button to heat...will that keep it in the heat mode...I am not familiar with all the programming ...But just want to heat and cool manually...
I'm reluctant to give programmable thermostat operating instructions for an unknown model, as the use of buttons and switches varies a bit. If you don't have an installation and operation manual for your thermostat you (or we) ought to be able to find one, at no cost, by seaching for it based on brand and model number.
Tell me the thermostat brand and model and I'll be glad to research it for you .
(Apr 30, 2014) Pete said:
I have an old unit that will not blow cool/cold air. I have had a tech out twice and I am trying to see if there are any things that I can check or ask my technician to check. The tech had the unit working properly, after his last visit, until about 2 weeks ago. At that time we had a cold-snap and I had to turn my heat back on. When I turned it back to AC it has not worked properly since. The outside unit (condenser) is running as is the air handler. Plenty of air is blowing out of the registers but it is only about 70-71 degrees.
I do not know anything about fixing ACs but I am pretty handy and I have been researching on the web. Some of the viable options I found are a stuck or bad Reversing Valve, coolant line could be blocked or contaminated or the Thermostatic Expansion Valve could be bad. Does that sound right? Any thoughts?
Also, I noticed that the high pressure line (small copper tubing, I think) coming out of the outside condenser is cold to the touch. Should that not be warm/hot? I really would like to get one more season out of the unit. PS: all filters are clean.
Found problem. AC was working but the emergency heat strips were stuck on. So the cold air was getting heated. Replaced and is working. Hooray!
Thanks for the follow-up.
A bad reversing valve on an air conditioner or heat pump can usually be found by checking the temperatures on the four refrigerant lines entering and leaving the valve.
Heat stuck on will sure do the trick. Your note will help other readers and I'll add your finding at our "too warm" article at
Also see REVERSING VALVE on HEAT PUMPS
(May 6, 2014) steve nelson said:
my a/c is running and blowing cold air and then on its on starts blowing hot air and cold air again this is a goodman heat pump.
Steve it sounds as if your compressor/condenser is probably working since you see intermittent cool air.
So perhaps there is a thermostat or control problem that is shutting off the compressor, OR the coil is icing up.
But as you can read in Pete's comments above, another explanation for an A/C unit that cycles between blowing cool then warm air can be a contol problem that is switching the emergency backup heat on - IF your system is a heat pump.
(May 14, 2014) eric said:
I just down sized unit to 2.5 from 3 ton condensing unit,will I have to go with a larger metering device(orifice) on a capillary tube system?
Eric Your system presumably already has a thermal expansion valve TEV installed. You will need to look at the valve brand and model, then review its capacity rating with the manfacturer's specifications for that device.
Some TEVs are adjustable. In that case you may be able to set the valve to perform properly. If not you'll need to change it.
For example, here is an excerpt from Danfoss's description of setting their TEV Setting
The expansion valve is supplied with a factory setting suitable for most applications. If necessary, readjustment can be made using the setting spindle on the valve. Turning the spindle clockwise increases the expansion valve superheat and turning it counterclock-wise reduces it.
For T /TE 2, one turn of the spindle produces a change of approx. 4K (°C) in the superheat at 0°C evaporating temperature.
For TE 5 and following sizes, one turn of the spindle produces a change of approx. 0.5K in the superheat at 0°C evaporating tempera- ture. For TUA and TUB, one turn of the spindle produces a change of approx. 3K in the super- heat at 0°C evaporating temperature
(May 21, 2014) Anonymous said:
My outside unit fan is barely turning. Air is not really cooling. Got a new circuit breaker because it was kicking immediately, now it doesn't kick the breaker but the fan is really slow...please advise.
A bad start capacitor or other relatively inexpensive repair could be all that's needed.
I would shut this system off. To avoid an overheated circuit and possible fire. Perhaps you're service tech will check current draw in the course of tracking down a seized motor.
4/25/14 Anonymous said:
Turn on air and it will run for a few minutes and blows cold but then cuts off and wont run anymore. Is a central H/A unit and heat works fine. Any ideas?
Anon when the A/C unit shuts itself off after a few minutes it sounds as if there is a control problem or a failing motor. Since you have heat that points to the compressor condenser unit. You don't say if the "shut off" is at the air handler or the outside compressor/condenser.
Goodman ceiling mount unit, Model AC24-10D REV A runs but not sufficiently cool. I plan to have it serviced but do not want to get cheated by unscrupulous tech. Where can I find info on this product. Goodman is no help--they say they no longer have manuals for this unit built in 2005.
Here is information about the Goodman A/C unit you asked for
This manual is to be used by qualified, professionally trained HVAC technicians only. Goodman does not assume any responsibility for property damage or personal injury for improper service procedures or services performed by an unqualified person. Service Instructions CKL, CLJ, CRT, CLT, TWC, CLQ & HDC Split System Remote Coolers and CPLE, CPLJ, CPRT, CPLT & HDP Split System Remote Heat Pumps with R-22 Refrigerant Blowers, Coils, & Accessories
You will also find some companies selling copies of A/C installation and repair manuals online.
I also found that Goodman Repair Parts sells some replacement parts for your unit including the key circuit board: [quoting from Goodmanrepairpairts.com]
PCBFM103S 300x300 Circuit Board PCBFM103S / PCBFM131S Goodman/Amana
This PCBFM103S circuit control board is a guaranteed genuine Goodman OEM replacement for several Goodman, Amana, and Janitrol units. All of our parts are shipped factory direct, giving you the assurance you need for a quality repair on your furnace, air conditioner, or other Goodman product.
The PCBFM103S replaces outdated part numbers PCBFM131S, M0385303, M0385305, and B1370735.
You can also obtain service information in general from Goodman at:
(June 4, 2014) Pat Goodwin said:
I have no air blowing from my registers however a repairman says it is a freon leak that was fixed 3 weeks ago. He says there is a pin hole leak again. That doesn't sound right since no air is blowing at all. Is he yanking my chain?
On the roof, there are 12 SEER 10 AC units for the central air for each unit. The small white compartment box is open and it says UP/DOWN - that you can take the cartridge out to shut the AC unit off. Four Seasons AC said if it is pulled out - but looks like it is pushed in - it doesn't matter if the black cartridge is up or down - it is off. BUT: they said the heat to the Rheem and the furnace fan should still go on even if the roof AC was off. The heat and the fan on the Rheem do not go on.
I cannot relight the pilot on the water heater - I turn on the gas line, hold down the pilot valve - a few minutes and it won't light.
I cannot find a way to turn on the Rheem Criterion II gas/AC unit. What else needs to be turned on? Thermostat (Honeywell) does not ignite the AC or fan or heat - but it could not possibly be the thermostat as the person who shut off the fan switch - also turned off the water heater.
Can anyone tell me how to get back on the furnace/AC in the closet - and did the bully per chance just take out the cartridge to the AC on the roof without worry of electric shock? If it is not pushed in - do people feel it is safe to just push it back in?
Four Seasons AC/Furnace said the AC circuit breakers are connected to the roof AC - and the furnace circuit breaker is connected to the closer furnace/AC.
(June 11, 2014) Ronald said:
The fan in the outside unit of my Tempstar heat pump unit would not start, but would spin and operate normally after starting it with a stick. The capacitor was bad and I replaced it. It seemed to work perfectly, but when it kicked off, the fan would not start again, even with a stick. I turned the unit off and waited a while. when I turned the unit on "cool", it started right up.
Ronald, perhaps the new capacitor is misfired, or the fan motor failed.also check the fan relay.
(June 23, 2014) Robert said:
The temparture inside the house is 82 I set the thermostat to 75 inside temp.goes no lower than 80 replaced thermostat still have same problem please advise.Thanks
Robert, best bet may be to run through the diagnostic sequence on the page above to see what is or is not actually running. Check for reduced air flow as well as too-warm air output. I suspect you need a repair tech but it would be embarrassing if we found the trouble were a dirty air filter.
(June 24, 2014) A/C shuts off after 5 minutes, blows SOME cold air when on... said:
First, let me say that I am a single woman with NO A/C experience. That being said... I took the panel off of the outside unit. I turned the A/C on from my thermostat. It kicked on, and it DOES blow out of my ceiling vents, and the air is cold.
It doesn't blow strong, but it does come out... I went back to the outside unit. I had 2 blinking lights on the pc board, and according to it, that indicates its "normal". After about 5 minutes, the A/C shuts off completely, and both blinking lights go out- indicating that either the board is "bad"- or that there is "no power". I live in Florida and it has been about 90 degrees lately, and my house (inside) has been about 85! The filter on the inside handler is clean. What can I do to get my A/C working again. I am on a budget :/
You've done a fine job of checking for the obvious snafus: your system has power and starts normally and delivers cool air at the registers. So I figure you're not faced with an obvious problem like a switch turned off. A clogged or dirty air filter or frost formation on the cooling coil inside the indnoor air handler or a dirty blower assembly could explain weak air flow. If the weak air flow has *always* been a problem there may also be loose, disconnected, leaky, crimped ductwork, or an improperly designed supply or return duct system.
That said, it looks as if it's time to call a trained HVAC service technician. Let us know what you are told or ask again if specific questions arise. What we learn will help other readers.
(Dec 1, 2015) Cindy said:
Heater was working just fine then I hear a clank noise as tho something was in unit the it stopped I drained the unit turned back on now it only like warm sometime in cooler side there is frost on bottom backside inside I let it set but won't warm the room.
Sounds like a bad control, relay, or motor. Have you given your service tech a call? What were you told?
(Dec 18, 2015) Anonymous said:
Compressor starts and stops n and off
Unless the cycling is rapid - seconds to just a few minutes, that's probably normal; else I suspect a pressure safety control is shutting off the system or there is a control, thermostat or relay failure.
(June 26, 2014) Anonymous said:
My ac unit keeps blowing fuses don't no what the problem is
Anon, when an AC unit keeps blowing fuses you should leave it shut down to avoid risking an electrical fire and call a repair person. I suspect a compressor motor is failing.
Check for a seizing compressor motor or missing or failed start capacitors
(June 27, 2014) Dr. Chandan said:
I have a carrier ac which is 10 years old Optima plus model. I am from India. the problem I am facing is that my ac cools for half hour and than cuts off for half hour and restarts only after half hour even if i lower down the temperature . I have called many technician but nobody is able to solve the problem . One person came and changed the compressor . technician says that there is no gas leak
I suspect an electric motor is overheating, going off on thermal reset, cooling down resetting. Also check for low voltage.
(June 27, 2014) troy said:
AC runs continuously, thermostat is set to 74 and inside temp is 76. AC does not shut off till late at night.. Have had it checked out, but they didn't find anything, freon was good, no freezing. Air is cool coming out of vents, but not cold.
To check that the level of cooling of air is reasonable please see AIR CONDITIONER TEMPERATURES
2014 - Barb said: when the air conditioning system is running we hear these clicky sounds definitely traced to the ductwork. [paraphrasing - Ed.]
Possibly the changing temperature is causing thermal movement in metal ductwork
A loose blower fan can wobble and sometimes nick or touch a nearby component also producing a clicking or ticking sound.
(June 29, 2014) LIZ said:
two things if your Air conditioner is not giving cooling
1; if Gas is not available in the Air conditioner system.
2: if compressor capacitor is out of order
first of all you should check your Ac compressor is running if running then check its gas. If compressor is not working ( and making sound as it is trying to on but fail.) then compressor capacitor should be replaced. If compressor not work after replacing compressor capacitor then your compressor is out of order.
(June 30, 2014) bill frame said:
i have a single unit the air starts cool then air warm
(July 6, 2015) Melissa said:
Air conditioning turns on,blows cool air, but never reaches desired temp...what could be going on? We havent turned on the heat in 7 yes..usually run the air conditioning for about a week in the summer...we turned it on bout a week ago..worked fine. Shut off during the day..ran it at night to sleep..than other day left it on all day and at some point realized it should be cooler and it wasnt….check settings, breakers...nothing wrong..what to do?
This question was posted originally at DIAGNOSTIC GUIDES A/C / HEAT PUMP
9 July 2015 Johnnetta Hamlett said:
Hi I woke up one morning to the AC blowing warm air. One time before it was the capacitor so we changed the capacitor that didn't work so we changed the contactor. This still did not work. However we can manually engage the contactor and the system will cool. Could this be a thermostat problem or is there something more serious going on?
Bill I think we need an onsite hvac tech to address your complaint.
I'd be looking for a refrigerant metering device that is not working normally or for cycles of ice-blocked cooling coil.
Melissa you need an on site service technician. Possible causes are a refrigerant leak, ice-blocked coil, crimped or damaged ductwork or other causes.
Above at INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS
you'll find an article titled LOST COOLING CAPACITY - inspectapedia.com/aircond/Air_Conditioner_Diagnosis.php
that can help you diagnose the problem.
Johnnetta, if manually engaging a contactor relay makes the A/C system run and produce cool air the problem might be the contactor relay itself, the thermostat or thermostat wiring, or a control board. Ask for help from your HVAC service technician.
(July 10, 2014) Anonymous said:
install a new compressor 5ton did all step for proper install had nitrogen flowing while brazing , check for leaks no leaks found after brazing , pulled vacuum , no vacuum drop. ect. filled compressor with r22 fill till showed 40psi on low side of gauge turn on compressor let it run for like 5minutes filled the to 40 saturation on low side hi side was showing 175 ambient temp 93degrees not cooling in side discharge air 75digrees what else can I do
Could you have a bad TEV or cap tube at the cooling coil?
(July 11, 2014) Anonymous said:
If the themostat is calling for cool,an the condensor motor don,t
Come on what must i check to see why the motor not coming on when the contactor is push in
Anon, start at the sequence of things to check at the top of this article and work down - they're in a rough order that should work for you. Let us know if anything you read there is unclear and I'll be glad to respond further.
(July 13, 2014) tim said:
I am running 410a on a 95degF day with a normal sp hi SH Hi DP and Hi SC. TXV inside
(July 14, 2014) Anonymous said:
Control board or sensor? Cooling compressor will not start with good call for cooling. No low power being delivered to pull in compressor contactor. Manual operation of contactor fires up compressor okay. [York Champion Heat Pump - 2 boards, one attached to thermostat in heat and blower compartment - the other in the compressor section with compressor contactor]
The "no low power" presuming the TT is working properly suggests a control board, right? But I'm flying blind here. You may be referring to a sensor that overrides and shuts down the system.
You checked for the obvious like a blower door switch open, right?
Yes, the blower operates fine so it cannot be a blower door sensor. It is only the compressor that does not come on automatically. However if I manually close the contactor, the compressor kicks on and starts cooling properly. Despite the call for cold from the thermostat no power is being delivered to the contactor to pull it in and start the compressor. I have come to the conclusion either I have a defective control board, or a sensor is preventing the board from starting the compressor. How can I test the sensors? Or determine if the board is the problem?
I agree with your guesses. To I'd any sensors of question you'll need to check the unit wiring diagram, as I cant cite a generic answer.
(June 30, 2015) NCK Bethesda Md said:
My Carrier heat pump A/C has stopped functioning. The repairman says that there is a condensate collection pan as a part of the indoor unit in the attic of the house and that a drainage line is plugged, and the rising water level in the pan actuates a switch shutting off the fan/compressor unit situated outside the house at grade level. He says that the pan unit needs to be replaced at cost of about $400. Is this diagnosis credible? Any alternate diagnosis and remedies?
This question was posted originally at DIAGNOSTIC GUIDES A/C / HEAT PUMP
Many A/C system air handler units include a condensate overflow pan switch that will sense a rise of water in the condensate pan and shut off the air handler unit. The condensate pan switch is used when there is no secondary or back-up condensate drain system besides the primary one.
Your tech says that the condensate drain line was plugged on your system. Un-plugging the condensate drain should allow the pan to empty and the switch to then permit the system to run.
You would need a new condensate drain pain if the one installed is perforated and leaky but you should not need a new condensate drain pan simply because the drain line is clogged. Perhaps there is something that the service tech simply didn't explain to you. Ask why the pan needs replacement.
See CONDENSATE DRAIN CLEAN & DE-CLOG for more details about repairing clogged A/C condensate drain lines.
(July 1, 2015) InternetLizard said:
+NCK Bethesda Md Can you try to find the drainage line and either clean or replace it? Sometimes there's also a pump that should be checked.
Thanks Liz, for the comment.
The proper repair is to clear the blocked condensate drain. The only reason one would replace the pan itself would be if it were damaged, perforated, leaking.
(Oct 10, 2016) Gino Ceravolo said:
I have turcott thermopompe and it is running but I don't have heat or cold air and thermostat is flashing 12 what's the problem with it
The error code 12 on some HVAC systems says you're calling for heat and not getting it: I suspect a failed fan limit switch or limit control.
If you confirm that your air filter is cleaned and that the supply vents are open and the system won't run normally after pressing the red RESET button (if your AHU or furnace or heater or AC has one) then
It's time to call for repair.
Continue reading at DIAGNOSTIC GUIDES A/C / HEAT PUMP or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or If your air conditioning or heat pump system has lost its cooling capacity or won't start select one or more of the diagnostic articles listed below.
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Also see REFRIGERANT DIAGNOSTIC FAQS
Also see REFRIGERANT PIPING INSTALLATION FAQs
(Feb 1, 2015) Avery said:
You've got everything covered except the price? How much does it cost?
I'm not sure what "it" is in your question. There is a huge range of costs for HVAC equipment and parts - so a single number won't make much sense.
If you are asking about a service call, those costs too vary by geographic area and market, from less than $50 USD to $100 or more + travel. There is also quite a range of markups that service companies apply to products that are used for repair or replacement.
What we might do is check the purchase price of specific parts used in a repair, but then too we need to consider how the HVAC service company prices their service business.
(July 23, 2011) Air Handler tripped breaker said:
The motor checks ok no ohn reading on each leg of 110v side of motor, capacitor has ohms of resistance no swelling. Either the mother board or the relay.
With power off, check first for shorted electrical wiring, next for a seizing motor or a motor with a bad start capacitor.
(July 29, 2011) Charles Gullette said:
I recently had a new 3 ton 13 seer unit installed. It included a new compressor, condenser, and cooling coils and digital non programable thermostat. The existing 3 ton blower and heater unit were reused.
After installation the blower unit starts, runs about 15 sec and then restarts. there is no effect on the compressor unit. My tech. says the blower is starting on the heater relay and then shifting to the cooling relay on the blower control board. He claims this is not a problem but that the board may need changed in the future. I did not have this problem prior to the new unit installation. Could it be the thermostat wiring or is my control board going bad??
Charles, I wonder if the new thermostat was wired exactly the same as the old one? And I agree that the circuit board could otherwise be the problem. I also agree that it's curious to have to change a circuit board after other components were swapped out unless either there is a compatibility issue (sounds wrong) or an accidental short circuit, or some mechanical disturbance that just pushed a failing component over its edge.
(Aug 27, 2011) AC making "revving up" sounds ev said:
When my AC (Trane) is running is sounds like someone is revving an engine every few minutes. The indoor part of the system is in the attic and when the "revving" noise happens the sound below, in the house, is like a "Blue Northern" strong wind.
Any thoughts? Thank you! NF
AC making revving up sounds
I'm not sure about revving up - perhaps a cycling of a motor trying to start? or a loose fan blade hitting something? AC making revving up sounds
(Jan 2, 2012) george said:
Hi new goodman h/p getting 0 psi on high side? help
sounds as if the compressor motor is not working at all
(Mar 24, 2013) james said:
i put t-stat in cool 24 volt transformer blew what caused this
Perhaps a short circuit in the thermostat wiring
my air condition is leaking water out of it
Look for a condensate drain clog or pan leak.
For diagnostic help see BLOWER LEAKS, RUST & MOLD
12/12/12 janie said:
my air condition is leaking water out of it
Look for a condensate drain clog or pan leak.
(July 11, 2014) Dave in Toronto said:
Singer incremental under window electric unit.
Compressor over heated and has seized. Tried Super Capacitor with no effect.
Replaced compressor. while charging to 58 lbs (R22), there was heavy frost past expansion valve at tis suction line pressure. No sweating of suction line. Compressor overheating. Changed filter/dryer installed a few years earlier. Retested. No change. Resting pressure was 250 psi. Changed expansion valve for new one. Much less frosting, but still evident at 58 lbs pressure after recharging. Now has new compressor, filter/dryer and expansion valve. No other components to change other than C coil. What's going on?
Dave, contamination may be fouling the TEV causing it to open or close erratically.
(July 12, 2014) Anonymous said:
My central air will go on than turn off in about an hour without cooling house down to set temp. There's a new motor, fan and pump.
Try the diagnostic procedures at
(July 19, 2014) Anonymous said:
question:jus changed the circuit board in my system...everything seems to be ok
except tht im not getting temperature control...checked room temp. using 2 different
thermocouples from digital meters...room temp stabilises at 20 degrees..upping set
temp.to 28 degrees and compressor keep
s running...temp.records at 20degrees on both meters..possible problem...can it be the evaporator sensor?
Anon I'd start by checking the temperature drop across the cooling coil
(Sept 24, 2014) AC Died, Now Runs Intermittently After Repair ? said
AC died in the middle of this horrendous hot spell. Ended up changing the compressor/fan capacitor and the contactor circuit board. Unit fired immediately when turned on and was putting out cold air. Unfortunately it will run for a couple of minutes then it shut down and will not restart until it sits for awhile. Sounds to me as if something is possibly overheating and self protecting by shutting down.
From just your note, AC, I can't make a useful guess. It's time to call a trained HVAC technician. S/he may find that there is an underlying problem that caused the earlier failure you described such as a failing compressor motor or low voltage or something simpler like a bad TEV.
(Oct 7, 2014) Joe Rouse said:
I have a Whirlpool Room Air Conditioner model WS092LW. Even if Whirpool no longer sells this model, where can I get info on the unit? Mine is moaning and ciculating HOT air! Suspect it's in need of coolant, but open to insight on this.
Joe, your AC unit may have indeed lost refrigerant. Don't just add more without also finding and fixing the leak.
12/4/2014 Anonymous said:
when I turn on my ac instead of cooling the heat comes on. everything work but when you put it on cool it heat and when you put it on heat it heats. is it my thermostat inside or something in the heat pump outside?
Anon if you are sure your thermostat switches are correctly set then I suspect a wiring error or a control board failure.
(Aug 7, 2014) tommy said:
the outside the fan motor stopped working after over heating so after putting in a new fan motor and capasitor i still have the same problem motor overheats then turns off repairman can't understand why this did not solve the problem
Check for low voltage, a control board or relay failure, or a wiring mistake.
Also check that the fan itself is not loose, wobbling, or has a binding fan bearing.
Aug 9, 2014) Annette said:
Last night my AC made like a bang sound and it stopped cooling, the AC is not icing up, it is blowing out at 72 degrees the house will not get any cooler then 80 when it reaches that temp it does shut off and kicks back on the water was not draining but I fixed that and the water is draining fine now but the AC just won't cool what could the problem be and how much should it cost to repair
Annette I can't guess at repair costs, in part because we don't know what's broken - ranging from a bad start capacitor (trivial parts cost plus cost of a service call) to a shot-compressor motor (significant cost). I'd give your service company a call. Let us know what you're told. Daniel
(Aug 12, 2014) Air Conditioning Repair Service San Diego said:
Thanks for sharing this informative blog on how to repair a broken air conditioner. This would help a lot.x
AC there are articles in this series that describe repair processes, basically beginning with accurate problem diagnosis. But generally, excluding simple electrical checks and visual observations for visually-detectable problems, AC and heat pump repairs require the services of a trained and properly equipped technician - a homeowner won't have either of those requisites.
Please see WINDOW / WALL AIR CONDITIONERS
(Aug 20, 2014) Anonymous said:
We have 32 condos in my building with a cooling tower outside , whenever the cooling tower shuts off due to electrical storms or service that requires tower to be shut down my Florida heat pumps shuts off and will not start again unless we do it manually . Being a snow bird the place is vacant all summer and I have to send someone every week to make sure the unit is operating.The unit is 3 yrs old and works well
(Sept 6, 2014) Nick Stull said:
Our townhome furnace/AC (gas heat, electric cooling) is not working properly, and the landlord has sent people out at least once to check this, and nothing is fixed. We turn it on, it kicks on and the outside fan and inside blower seem to be working properly. A couple of hours later, the unit will have cooled our place a total of a couple degrees (from 78 to 76 in one run), before it stops cooling. After that, the temperature in our place gets stuck, and the airflow in the downstairs vents slows to basically non-existent, and we have absolutely no airflow in the upstairs vents. Any advice on what I could tell them to check for? And while it is a complete waste of money, is there any harm in me keeping the A/C on so they actually experience the problem, or will this aid at all in diagnosing the issue?
(Sept 9, 2014) Anonymous said:
A/C is not cooling...Compressor is running...pressures are all reading good...inside coil is clean but not getting cold...low side Freon line is not getting cold or sweating...high side line is warm...any idea what the cause is..??
Look for a refrigerant leak, low refrigerant, ice-clogged cooling coil
(Sept 7, 2014) Nick Stull said:
Additional information, which may or may not narrow down the problem: After leaving it off for a while (hoping it would start working after giving it a break), we can hear (intermittently) water dripping down the drain pipe, at times a somewhat significant amount. But even if it was ice clogging the cooling coil, that would only indicate another set of issues it could be, among which would be either low or leaking refrigerant, right?
Your note further suggests ice-blocked cooling coil troubles.
(Sept 9, 2014) Anonymous said:
I have had a brand new 4 ton heat pump 15 seer unit installed. I had a 4 ton 12 seer 20 year old unit removed. My new unit is costing more per month than the old unit. had a new thermal expansion value installed ,did not solve problem . they want to put a solvent in value cuzz they think a rust inhibitor is causing value to not work proper. Am going on 4 months can't afford electric bill.Should I go with another unit or try the solvent
Start by getting an accurate diagnosis of the trouble: the behaviour of the cooling system, its ability to bring the house down to the set temperature, and don't forget to check for any and all problems that could be interfering with its operation. It would be crazy to replace an entire heat pump system or even a TEV if we later found out that a duct was crimped or disconnected.
(Sept 21, 2014) Anonymous said:
the air conditioning run well in winter mod but not in sumar
in sumar mod the compressor Heats up and stop work no Noise Not used
(Nov 26, 2014) Michelle said:
Heat mode works fine.
In cooling mode, air is blowing but not cooling.
Can reset breaker even though it isn't tripped and will start cooling again.
Noticed more frequently as outside air temperatures got cooler.
Seems to happen daily or every couple days, but all I do is reset the breaker and it works again
(Dec 27, 2014) scott said:
AC cooling works fine. Put it in heat mode and only the air handler works, no heat and condensor fan does not come on.
Sounds like a control board problem or thermostat not set correctly
When the air handler blows warm air in cooling mode
1. check that the aux heaters are not stuck "on"
2. check for a warm cooling coil - which in turn means lost refrigerant or a refrigerant metering problem or a failed compressor
When re-setting a breaker is "fixing" the problem I suspect a failing compressor motor.
If the outside heat pump unit is not turning on there may be a failed control, relay, or even thermostat wire connection.
(Sept 24, 2014) Anonymous said:
for 2 days the lights in the house dimmed for longer then normal before compressor kicked in 3 day no cool air?
Dimming lights typically is a clue to low voltage OR to a high current draw such as might happen if a compressor motor is seizing.
(Sept 25, 2014) ron said:
thanks danjoe . the unit is only 5 years. iam hopeing its not the compressor but something causing the low voltage. thanks again ron
Thanks for the follow-up. If you monitor voltage right at the meter or panel that can confirm low voltage from the electrical company. Rule that out to start. You might get the motor running with a new start/run capacitor.
(Sept 26, 2014) Anonymous said:
thanks for the info dan. the ac guy showed up yesterday took the cover off went directly to the run cap. put a new in checkd Freon 20 min. later handed me a bill for 172.50 had I known I could have done it myself. knowledge is power. and MONEY. still not sure they go out thanks again.
(Sept 26, 2014) Anonymous said:
thanks for the info dan. the ac guy showed up yesterday took the cover off went directly to the run cap. put a new in checkd Freon 20 min. later handed me a bill for 172.50 had I known I could have done it myself. knowledge is power. and MONEY. still not sure they go out thanks again.
Sept 29, 2014) Roger said:
We have a 'heat pump', the outside unit starts up when required, how ever, the inside blower does not always come on. It works ok sometimes, but not always. When working normal, the temp is great.
(Oct 9, 2014) Ronda said:
We have a heat pump/ air conditioner unit. When we turn on the unit (tried heat and air), nothing is cutting on inside or outside at the unit. We have a Honeywell RTH6350D programmable theromstat and changed the fan from auto or on and even that is not working. Any suggestions on what could be the problem?
I'd start by confirming that there is electrical power to the devices. Also check for an open blower door or a condensate overflow pan that is full.
(Dec 8, 2014) Sharon L said:
Hi, I have a 10+ year old York electric ac/ heat pump. My heat was on (but the "heat on" notation on my thermostat didn't read that it was on and the fan kept running for hours. Is this normal? I am just wondering why the fan kept running while the house was not being heated---or not according to my thermostat anyway.
Sharon if the heating system fan runs indefinitely I suspect that at the thermostat or at a fan limit switch the fan was set to ON rather than AUTO, OR the system was unable to reach the thermostat set temperature - a problem that deserves a service call.
(Dec 16, 2014) Andy said:
We have an ac/heat pump. Condensation is running down the side of the unit from about 3/4 way up, then running off the roof, so much so it leaves a lg puddle on the patio. When the unit runs and shuts off this stream is constant but slows to a drip if the unit has not run in a while.What could be the problem or is this normal. I don't recall this happening in prior yrs
Andy it sounds as if the normal condensate handling system of your unit is not working, perhaps due to a clog or a rust perforation. It's not normal to see water running on the outside of the unit. Ask your HVAC service company to take a look. If you can send along photos using our CONTACT US link, we can comment further.
(Jan 5, 2015) George Kubo said:
Heat Pump fan comes on when you turn on the thermostat for heat but goes off after a minute. There is 24 volts on contractor relay coming from the control board when the fan is on BUT there is not 24 volts coming out of the control board to the contractor relay when the fan turns off. Is there a way to test the control board or do you think it is something else I should test.
I agree that it sounds like a control board problem. For someone not an HVAC tech a reasonable start is a close visual inspection of the board for loose or burned components.
(Jan 5, 2015) kevin said:
The condensor fan in Heat has not spining so I'd replaced the capacitor but it didn't work as well. So I tested it in Cool and it blowed a cool air. I assummed that the air conditioner would not work as well. I am confused what's happing on my heat pump. Thanks for in advance.
Kevin I'm confused too. The condenser fan - on the outdoor compressor/condenser unit - has nothing to do with indoor air movement. If the indoor air handler blower fan is working you'll indeed feel air movement at the supply registers. The temperature of that air depends - if your system is a heat pump and if there is backup heat that takes over in very cold weather, then in heating mode you'd expect to feel warm air at the supply registers.
(Mar 9, 2015) Anonymous said:
i have a heat pump unit that works on heating mode however on cooling mode it gives a low suction pressure it is an r410 split unit. eventually icing up the evaporator coil
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