Condenser Fan Won't Start FAQs

A/C & Heat Pump Outside Compressor/Condenser fan won't start or won't run

HVAC Compressor/Condenser Fan Won't Start Running

Diagnostic Starting Point:

• CONDENSER FAN WON'T START

Mini Split Condenser Fan Motor Sticks & won't Turn On Unless Power is Off

I have a Gree mini split unit that is throwing an error code related to the condenser fan. I. Notice that the shaft of the fan motor is sticking when I turn it manually. This sticking is preventing the fan from turning when it's on during normal operation.

I notice when I unplug the motor from the main circuit panel that sticking goes away and the shaft turns like normal.

There is no electricity going to the unit. The breaker is off and the disconnect is unplugged. Am I looking at a circuit board issue or a fan motor issue? - On 2021-02-20 by David

Reply by (mod) -

@David,

That sounds like a motor failure, perhaps a bad bearing. When power is being applied and the motor is torqued the bearing may be binding.

Also see AIR CONDITIONER WON'T START

 

When should the outside condenser unit turn on?

When the a/c kicks on, is the fan on the outside condenser supposed to come on right away, or does it come on a few minutes later? On 2012-09-08 by Pete H

by (mod) -

Pete,

The behavior you describe is normal for some AC / heat pump systems.

As long as the fan continues to run, is not making an unusual noise like humming or rattling you should be ok.

 

Question: buzzing in the outside compressor/condenser unit

The fan want run on air conditioner outside unit. It just makes a buzz sound - Joe Russell 5/23/12

Reply:

Joe: could be a bad fan relay or start capacitor; Does the compressor itself try to start?

A snake got caught in my compressor unit fan

After I turned the AC off for about an hour it came back on.

A snake got caught in my fan and stopped it for several hours it seems. Now fan will not spin and can't hear any power getting to outside unit? 2018-09-07 by Mark Kennedy

Reply:

Mark

Nice going. I'm glad the system re-set itself when the fan motor, probably overheated being bound up by a snake who was surely upset as well, cooled off and re-started.

Let me know if you or the snake have further questions.

Carrier unit condenser fan will not start

I have a Carrier unit. At times the condenser fan will not start. After I power cycle the unit the fan will then work correctly for a couple of days then stop. I power cycle the unit again with the same result. 2019-06-06 by Joe

Reply:

Joe,

In the ARTICLE INDEX you'll find a diagnostic and repair article on fan will not start. Most often after checking for a bad connector or wire the service technician will try replacing the starting capacitor.

 

Condenser Fan does not come on when heat pump turns on in heating mode

My furnace has a heat pump. When the heat kicks on the outside fan may or my not come on.

I figured this out because I could hear a funny noise from my heater. I could feel alot of heat and it was quite warm to the touch. It was overheated.

I immediately came back up and turned it off.

I left it off for several minutes and turned on and bundled up to go outside and the outside fan was humming and the fan was not running. I waited for a few minutes and as I turned to come back the fan kicked on.

This fan has always come on when the furnace kicks on. I didn't know what to do but to come back in and turn it off. Ive just had a hot water tank to burst and destroyed pretty much everything in my basement. I don't know if that has anything to do with it or not. Im really struggling because I found out my insurance isn't worth much.

It wouldn't pay for the HW-Heater or the plumber. Cut the value of my carpet in half. I don't know if they would do anything about a hot water heater and my deductible is outrageous. Im struggling and searching you tube hoping there might be something simple I can do until I can do better.

This heater sits in the same closet where the hot water tank sits. They were side by side. There was probably 4 or more inches of water running out my basement door. The room where it happened has no doors. That room is huge.I need help! Anybody have any ideas? - On 2020-12-06 by Lois

Reply by (mod) -

Lois,

That sounds a lot like an electric motor that's having trouble starting.

Particularly if a control or motor got wet from the previous event in your home it may have been damaged. Do you know if any electrical components were supposed to water or high moisture?

Fan Controller Keeps Condenser Fan From Turning On When It Should

Hello, I recently replaced my OEM fan and run capacitor after having it troubleshot by local AC repairman, who said the voltages to fan were good, so it had to be the fan (right). Fan still doesn't run. It's a 2 speed fan, so I purchased the OEM motor to replace it.

I have: Replaced motor (spins freely, OEM, correct connectors and voltages labeled), replaced capacitor, checked breakers, checked contactor, all seems good.

The only thing different I can tell is that there is a fan speed controller between the contactor and fan.

I pulled the fan connector apart and checked voltages, red lead was hot whether contactor was on or off, the other 3 leads all stayed zeroed out regardless of contactor position

Could this be a controller failure? Thanks. On 2020-06-20 by T Jones

Reply by (mod) -

Nice going TJ

Yes it sounds to me like either a wiring error (perhaps at the controller) or a bad controller.

Compressor condenser fan not working, compressor is humming, trips circuit breaker

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

Reply:

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.

Follow-up from Johnny:

put hard start on and it running again thanks for all your help - Johnny

Condenser unit fan startup troubleshooting - fan starts slowly or stops completely

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.

Reply: check the fan contactor, the circuit voltage and current draw when the compressor is starting; possible control board trouble?

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.

Reply-DF:

Clarifying:

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?

Goodman fan and compressor don't come on in Florida

Have a florida heat pump system...Goodman..fan and compressor doesn't turn on...

replaced capacitor...still doesn't turn on...checked all circuit breakers, etc..did find a frayed wire ( black ) that plugs into the contactor..cut the bad part out and replaced the spade connection...still doesn't work...thermo. is set for 70 degrees..temp. inside is 78 ...

seems like there is a reset or fuse somewhere that is bad...no noise or humming etc...Not sure where to go from here... 2016-10-31 by Ken C. allbsdd@aol.com

Reply:

Or could be a bad control board or relay. I'd start by confirming that there is electrical power to the unit.

Watch out: you could be killed by electric shock. If you're not trained to fool around with the compressor/condenser unit and its wiring I'd recommend hiring a service tech.

Fan won't work on the outside unit

My fan won't work on the outside unit, what could be causing this? 2016-07-17 by Ethel

Reply:

Ethel, probably the problem is one of those discussed in the article above - you're on the right page.

OF course start by confirming that the outside unit has electrical power and your thermostat is calling for cooling.
Your service tech will check for:

- a bad fan start/run relay

- a bad fan start/run capacitor

- a failed fan motor

 

Condenser Fan motor in outside unit went bad, replacement fan is different

Fan motor in outside unit went bad and installer used different fan motor than came on unit when new

Now the fan is lower in unit 2 or so inches and system seems to not cool house as easy any thoughts on this one end of season now. 2016-09-29 by Anonymous

Reply:

Anon:

If the replacement fan motor meets the operating specs of the original one it should be OK. Moving the actual fan blades inside the condenser unit might indeed change the airflow pattern enough to be worth thinking about.

For example a typical condenser fan draws outside air IN through the condensing coil around the sides of the unit and blows the heated air UP and OUT at the top of the unit. If changing the fan assembly caused some of the exiting air to blow against the upper sides of the condensing coils you'd be reducing their effectiveness.

If the condenser unit is less efficient than it was before it might have to work harder and longer. But I think your tech will look elsewhere if the house is too warm.

Reader question: condenser fan motor and compressor stopped working

I have the Worry Free insurance on my outside AC Unit. It's an old unit! It's an Armstrong unit that is 20 years old at least. The condenser fan motor stopped working. The compressor stopped working also.

Worry Free came and replaced the condenser. Still nothing. Ordered a new fan motor and replaced it. Still nothing except now the compressor works! Fan not working but compressor is . . . could the wires be crossed? Could Worry Free have installed the new parts wrong? 2017-10-23 by Frank

Mod reply:

Frank,

You ask a completely fair question but not one I can diagnose from just this e-text. Certainly if the condenser unit fan isn't working do not run the compressor motor as overheating can damage the system.

When you say they replaced the condenser - I'm not sure what was replaced - not the compressor motor, right?

If the fan isn't working typically it's one of the problems discussed on this page above: a bad control or relay, even a loose wire or connection, or a bad fan motor or bad fan start/run cap.

Those are things a tech would typically have checked. You might ask the service manager to send out a senior technician in hopes they can stop losing money by repeated repair calls.

Keep me posted - what you find will doubtless help other readers.

Follow up:

1st . . . nothing worked. Only a hum like it was trying to turn on, but fan and compressor didn't work. Next the condenser was replaced. (silver, about 4 inches long, snaps in to place). Fan and compressor still didn't work.

Then another tech returned with the new fan motor. He installed that. Fan still not working, but compressor did fire up. I know you can't give me a complete diagnosis, just wanted to give you the facts. Thanks!!! I'll keep you posted.

What will make an air conditioner or heat pump compressor motor heat up and turn off

What will make a motor heat up and turn off - On 2011-05-15 by Anonymous

by (mod) -

Assuming you refer to an air conditioner compressor/condenser unit compressor motor that is overheating and shutting down, the bad news is that the compressor may be seizing and at end of life.

There are other things the service tech will check out first including the voltage level and current draw, and the refrigerant charge.

S/he may also check the starter and run capacitors and even the installation location for sunlight exposure and adequate airflow around the unit. Let us know what is decided as it may help mother readers.

Question: condenser unit fan won't run

I replaced the fan motor and capacitor on my unit and now the the fan won't come on. I've checked wiring several times and can't find any reason it not to start. 2018-06-01 by George

Reply:

Check the fan motor removed from the unit - that will tell you if the problem is the fan motor, bearings, capacitor, or the control board, relay, wiring.

Question: ac condenser fan will not power on

My ac condenser fan will not power on. I replaced the capacitor. Swapped out the fan motor into another unit - it worked fine. Cleaned the contactor contacts. Compressor starts/runs.

Any ideas as what to do next? The unit is a ten year old carrier unit. 2018-03-13 by Alan

Reply:

Since we trust that the fan motor is OK the problem is most likely the fan relay or in the control board or in a wiring connection.

Question: heat pump (outdoor unit) cannot start

Fan does not run! Room blows out cold air and runs constantly, blowing cold air! Why? 2018-01-28 by Anonymous

Reply:

Sounds as if the indoor blower fan works but your heat pump (outdoor unit) cannot start - could be because of very low outdoor temperatures, combined with a failure of your backup heating system. I hope you called your HVAC tech for repairs.

Question: bad fan relay or frozen fan motor

I have also checked relay on board and fan gets 110 signal from it

Why would my condenser fan not run if I have checked capacitor and motor and all check good. I manually engage contacts and compressor comes on but fan doesn't run even with a nudge with a stick. 2018-07-22 by Greg

Reply:

Greg:

Sounds like a bad fan relay or frozen fan motor.

Question: A/C not cooling, condenser fan not running

Several days ago I noticed that even though my air handeler was running the AC was not cooling, I foudn that the condensor was not turning, I flipped the breaker (that apprered to be in the on position) and it worked for awhile.

15 minutes later I noticed that the condenser was not operating again so I flipped the breaker again it corrected the problem. I then went on the replace the breaker which seemed to correct the problem, the AC worked normally for several days.

Now I find the condenser is not working again and flipping the breaker fails the correct the problem. When the condenser was working it was providing good normal cool air.

The system is 2 years old. I assume I have an electrical problem in the condenser. What is likely to cause this problem and how can I test for it (I have a test meter) but I want to be careful because I know that a coil can retain a dangerous electrical charge even when all power is off and disconnected. - Rick 7/13/12

Reply:

typically we see if the fan spins, if it has power, and if the controls and fan contactor are bringing power to the fan when the condenser unit starts up.

Reader Followup

My problem turned out to be a bad contacter (damaged by ants) - Rick 7/13/12

How to diagnose an HVAC condenser unit fan that won't start

5ton trane condenser. Fan motor is intermittent. Condensor short cycles because fan doesnt start. Can be pushed to run.

Recently put new thermostat. Wired like old one which was instslled with old unit. Not sure if there was a heat pump. ..but this unit has heat pump. Red wire to R & JUMP PIN to RH. Is this a problem with internal circuit board in condensor/ heat pump. And causing conflict in signals? Just had service to condensor.

Oiled/ lubed fan shaft bearing - fan is still squeaking on start up. Til it warms up a bit

Put in new capacitor. As well as new thermostat. What else could be causing intermittent issues with fan.

Rough starts /push blades to start after its off for awhile. Can run fine 1-2days ( hi80°s) then fan fails AGAIN? AC been on for 1 mo.

These issues been going on 2 wks. Even after the new parts. Never sure if fan will start - On 2020-04-13 by Anonymous

by (mod) -

Anon:

Here are three HVAC fan diagnosis and repair articles that will guide you through diagnosing and fixing an intermittent condenser fan problem with intermittent fan failures.

Before getting too detailed, check for

- a loose or corroded wiring connection

- a bad fan control relay

then see the diagnostic suggestions at

FAN, COMPRESSOR / CONDENSER UNIT
and

ELECTRIC MOTOR DIAGNOSTIC GUIDE

and also, though it's for the indoor handler, see the additional fan diagnosis at

FAN WON'T START

Let me know what you find as that may permit further suggestions and also may help other readers.

AC condenser is buzzing and fan not running

AC condenser is buzzing and fan not running - On 2020-05-25 by Roland -

Reply by (mod) -

I would leave power to the unit off. I can't tell from just the comment whether we have a bad relay or failed compressor or control.

Condenser Unit Fan stopped working, but the Compressor was Wtill Running

Just replaced fan motor, replaced contact capacitor, new air filter. AC was running fine for a week, then the fan stopped working, but the compressor was still running. Now when I turn my air on, the fan runs for 15 seconds and shuts off with the compressor still running. Any ideas? 2018-06-13 by Anonymous

Mod reply:

Sounds like a bad fan relay. Check for a connection that's opening up when the motor heats up.

Compressor starts, fan doesn't start, I hear a hissing

My compressor turns on but the fan does not turn (I can turn the blades by hand) within 10 t0 15 seconds I get a long a loud hissssssssssssssssssssss.

I have some more info on my a/c when the a/c is turned on by dropping the temp in the house the compressor turns on but the fan does not turn, if you start to turn the fan by hand it starts spinning.

When I turn it off by picking up the temp it stops.

When I drop the temp again nothing goes on. If I wait a few minuites and try it again the compressor starts but the fan still has to be started by hand. Thanks for any help you can give. Thanks for you help - Henry

Reply:

Henry I suspect a bad fan start-run capacitor

But see the diagnostic suggestions at

• HISSING SOUNDS, HVAC from A/C or heat pump system

A/C not cooling, condenser fan not running - ants damaged a contactor relay switch

Several days ago I noticed that even though my air handeler was rinning the AC was not cooling, I foudn that the condensor was not turning,

I flipped the breaker (that apprered to be in the on position) and it worked for awhile. 15 minutes later I noticed that the condenser was not operating again so I flipped the breaker again it corrected the problem.

I then went on the replace the breaker which seemed to correct the problem, the AC worked normally for several days. Now I find the condenser is not working again and flipping the breaker fails the correct the problem. When the condenser was working it was providing good normal cool air.

The system is 2 years old. I assume I have an electrical problem in the condenser.

What is likely to cause this problem and how can I test for it (I have a test meter) but I want to be careful because I know that a coil can retain a dangerous electrical charge even when all power is off and disconnected. - Rick

Reply:

typically we see if the fan spins, if it has power, and if the controls and fan contactor are bringing power to the fan when the condenser unit starts up.

Reader Followup

My problem turned out to be a bad contacter (damaged by ants) - Rick

New AC unit, has trouble starting up / compressor fan won't start

My air conditioner is new. It's been hardly four month since I purchased it. most of the times it tries to start 2 to 3 time and then get started and some times unable to start

I dont have stablizer in my house for ac. when it runs it runs smooth and when it trips same case occur like starting can you please comment the possible casuse - Waquar Zaidi

Took the top off the unit. The fans spins by hand but wont turn on and run. Could it be the condenser? - (July 20, 2015) Lewis

Reply: If the compressor motor runs but the compressor/condenser fan won't run

see FAN, COMPRESSOR / CONDENSER DIAGNOSTIC FAQs and check for a bad fan start run capacitor or a bad fan relay.

Wagar I'm surprised to read that a new A/C system compressor is not starting, but I suppose it could be a bad start capacitor or another bad control such as the Thermostatic Expansion valve.

There are perhaps a few mistakes that could happen during installation that could destroy even a new A/C compressor such as dirt in the system or an improper refrigerant charge or a bad TEV that slugged the comprssor with liquid.

I'm unclear about the second and third sentences of your question.

Reader followup:

2nd and 3rd sentence I would like to elaborate: when compressor starts its working fine I mean it cools the room I use to run it on 26 degree centigrade and when thermostat trips and after 10 to 12 mints when compressor again tries to start same problem comes. and some time with out problem, compressor starts in first attempt.

is this a compressor problem what will happen if I continue to run my ac in this situation. thanks in advance

Reply:

AHA Wagar,

I can't pretend we can really diagnose by e-text Q&A, but if I understand more clearly, you are saying that the A/C compressor starts and runs OK the first time, but after the thermostat is satisfied and stops the cooling system compressor/condenser, when the temperature in the building rises and the TT calls for cooling a second time, the compressor is having trouble starting.

A simplistic view would be to treat it as a "hard starting compressor" and install a hard start capacitor kit. But since the compressor starts OK cold, it might be a different trouble.

If the compressor is trying to re-start against high head pressure that is more difficult than starting "cold" when the refrigerant pressures are the same on both high side and low side of the system.

So I'd look into what would cause head pressure to remain high after the compressor stops running. In many HVACR systems, as soon as the compressor stops running the pressures begin to equalize on the two sides of the system.

See

COMPRESSOR / CONDENSER DIAGNOSTICS

HVAC COMPRESSOR WON'T START

For more diagnostic help see the article

REFRIGERANT PRESSURE READINGS & CHARTS

and REFRIGERANT PRESSURE CONTROLS & SWITCHES

Reader followup:

it even having same problem in first time start and now these days after its thermostat satisfies its not restarting after several attempts.

what I am concerned is: is it a compressor problem? or capacitor. or possibly some thing else when ac start it works fine I am as far as cooling is concerned there is no problem with cooling once it get success in starting. - Waqar

Reply:

Waqar why don't you try a hard-start capacitor kit

Reader followup:

Thanks Mod, will definitely try actually I am away from my home town will reach in 15 days. I would like to thanks you for your support you provided and will let you know the results.

Is the problem with the fan motor or the compressor motor in my condenser unit?

I've a Lennox outside a/c unit. The fan/motor and compressor are part of the unit. The fan was not spinning and the A/C is not running.

I've isolated the problem down to the fan/motor or the compressor, but don't know how to check or find out which it is.

Any idea on how to check if the fan/motor is 'bad' or the compressor is 'bad'? - Fan or ... 7/23/11

Reply:

Fan or compressor: you could also have a bad control board, or relay switch in the compressor/condenser unit.

If the fan is bad and the compressor is OK you'll hear the compressor turn on at the start of a cooling cycle, though a bad fan and system overheating could later cause some compressors to turn themselves back off. Similarly, if the compressor is bad your fan motor would still run.

So I'm suspecting a control or switch problem.

Should my compressor ever run without the condensing fan running

Should my compressor ever run without the condensing fan running?

I have a 2 ton Heil central air unit.

I have worked on automotive AC, Automotive unit work done always had the condenser fan come on at the same time or shortly before and stop at the same time or stay on shortly after the compressor. does not seem normal to me. - On 2018-05-29 by Steve

Reply by (mod) - no

Steve,

I agree with your AC experience. I

f the compressor runs and the condenser unit fan does not, nothing is cooling the high pressure high temperature refrigerant gas down to a liquid and the system won't work.

I'd look for a bad fan relay, motor, or run capacitor, or even a bad control board.

The fan on my A/C condenser unit continues to run after the cooling stops. Condenser unit won't stop running.

The fan on my A/C continues to run after the cooling stops. I have a temp probe in a vent and watch the air temp climb until the next cooling cycle and the temp drops again.

This symptom is not consistent, because often the fan shuts off about a minute after the compressor stops. What I have noticed is that when the fan continues to run, the compressor also seems to be running, which doesn't make sense because the vent temp is rising.

Perhaps it's just the compressor fan that continues to run, not the compressor itself. If the compressor fan runs, would that keep the blower fan running? On 2019-06-08 by Rick Z -

Reply by (mod) -

Sometimes when a fan keeps running it's because the system is entering a defrost cycle. However I would expect the compressor to stop.

by Rick Z. Both blower motor in air handler indoors and compressor fan on the condenser outdoors keep running

Just to clarify... The blower motor in the furnace keeps running even when the cooling has stopped. However, the compressor fan is also running without providing cooling. This is happening frequently, but randomly, throughout the day.

Also, this new system, installed last August 2018, has never been able to get the humidity lower than 60%. In fact, while it cools the condominium well, the humidity will actually sometimes rise while it's running.

Now I suspect that's because the blower fan is running after the compressor has shut down, thereby taking residual moisture off the evaporator coils and returning it back to the home.

The system is sized correctly @ 2 tons blowing at 850 cpm, for a 1700 sq ft condominium on 2nd floor of 4 story building.

by (mod) -

Rick I think we have several things mixed up here. The outdoor compressor fan does not remove Frost from the indoor evaporator coil. It's air movement across the coil that does that.

In general if a air conditioning system can't get the humidity level down then the system has been oversized. Course there could be other problems such as a cooling coil that's becoming blocked by Frost or dirt. Sounds like you need a competent service tech on site.

The heat pump compressor stops but the condenser fan keeps going: OK?

Compressor runs for 30 minutes and stops, but the condenser fan is still going.

The heat pump compressor won't keep running - condenser fan still going - 2018-05-21 by Mark

and

Hi - My condensing fan continuously runs even with the thermostat off . What could cause that to happen ? - On 2018-03-23 by george Perry

Reply by (mod) - that's normal

Mark

It's normal for a compressor to stop while the indoor air handler continues to run in SOME situations such as a cool down cycle at the end of a run cycle.

Depending on the cooling load, the compressor may cycle on and off while the fan keeps going.

But if the outdoor condenser unit fan keeps going for hours after the condenser has last run, then something's probably wrong with:

• the fan relay
• shorted wires
• a bad control board the control board in the unit.

Alternatively, if by your notes you mean that the compressor won't run enough to produce cool air, indeed you need repair.

In that case the cause is not something I can diagnose from a brief e-text. It's time to call an HVAC service technician.

Is the problem with the fan motor or the compressor motor in my condenser unit?

I've a Lennox outside a/c unit. The fan/motor and compressor are part of the unit.

The fan was not spinning and the A/C is not running.

I've isolated the problem down to the fan/motor or the compressor, but don't know how to check or find out which it is.

Any idea on how to check if the fan/motor is 'bad' or the compressor is 'bad'? - Fanor

Reply:

Fan or compressor: you could also have a bad control board, or relay switch in the compressor/condenser unit. If the fan is bad and the compressor is OK you'll hear the compressor turn on at the start of a cooling cycle, though a bad fan and system overheating could later cause some compressors to turn themselves back off.

Similarly, if the compressor is bad your fan motor would still run.

So I'm suspecting a control or switch problem.