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Photograph of This new compressor was placed directly against a brick wall. One third of its condenser coil cooling ability was blocked. HVAC Compressor / Condenser Fan FAQs #3

A/C or Heat Pump Fan Condenser Unit Fan diagnostic questions & answers - FAQs No. 3.

More questions & answers help diagnose problems with the air conditioner or heat pump condenser unit fan

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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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

More HVAC Compressor/Condenser Fan Diagnostic FAQs

Air conditioning compressors overgrown with shrubs (C) Daniel Friedman

These questions and answers were posted originally

at FAN, COMPRESSOR / CONDENSER UNIT - be sure to see the repair advice at that page.

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.

On 2018-09-20 by (mod) - can you use your A/C as a fresh air vent fan?

Carolyn

Sorry to be vague but ... as Mark Cramer says: It Depends.

If you are running a window AC unit AND if the window unit has a control that will admit outdoor air, then yes you can run the unit in fan mode and blow outdoor air into the home.

If you are running central air conditioning AND if your central AC system includes an outdoor air source you can do the same. But that would be uncommon in residential air conditioning systems.

So in my third case, sorry, but no. If you have a typical home central AC system and you just run the blower fan alone, it will circulate air and thus may make the building a bit more even in temperature but it won't be bringing in fresh outside air.

What I do, when the weather is suitable, is open a window and stick a box fan in the window, blowing IN.

In a prior home that had a whole house exhaust fan we had a better solution: when it cooled off outside we'd open windows downstairs, then turn on the whole house exhaust fan that drew outside air in the windows, up through the house, and out through the attic and roof exhaust.

On 2018-09-20 by Carolyn Reese

all I want to know is how to get new air into a room without the AC running. Can the fan be used for this?

when the AC is off and only the fan is running, is the fan just moving air around in the room or is it replacing the air in the room?

On 2018-09-08 by (mod) - a motor can be bad but check out OK on the bench when it is not running.

MP

Regrettably yes, a motor can be bad but check out OK on the bench when it is not running. That's because when the motor gets up to speed a wire can open due to the centrifugal force exerted on the rotor -the rotating component in the motor.

If a motor hums and won't start a common inexpensive thing techs try is to just replace the starting capacitor or to install a hard-start capacitor. Search InspectApedia.com for HARD START CAPACITOR to see details.

On 2018-09-05 by MPG

Is it possible for a condenser fan motor to be bad even if

1)the windings ohm out correctly and

2) there are no shorts of the leads/windings to the case?

Motor shaft turns freely, no wobble, slight in and out play on the shaft, maybe 1/4" to 3/8".

I was out of town when the AC quit. Tech told my wife the capacitor was bad( it does check out bad) as well as the fan motor. She made him leave the old parts, so I checked them. Comments?

On 2018-08-18 by (mod) -

VW

some possibilities include a loose connection, a bad capacitor or wrong value capacitor, low voltage, or failing motor.

less likely a loose fan blade

On 2018-08-17 by valleyworld25

I replace condenser motor and capacitor fan spins slow what could be causing this

On 2018-08-09 by (mod) -

When a fan runs backwards it's mis-wired (or has been struck by lightning); It sounds as if you are perfectly on top of the wiring directions to reverse fan direction.

If that's not working but the fan ran fine in the wrong direction I don't suspect the capacitor I suspect a wiring error such as an inadvertent short or internal damage in the motor. Sure it won't hurt to try the old cap.

Watch out: as you may know, making a mistake can shock you or kill you.

On 2018-08-08 by JJ Smith

Older Bryant A/C. The condenser fan finally failed. Found a replacement Motor and Capacitor from NA and installed. Motor fan is running backwards (pulling air in top, thru the coils and out the sides.

Motor was equipped with stacons on the orange and yellow wires and you are supposed to disconnect them and connect both orange to yellow to reverse rotation. Reversed wires, still rotates the same direction.

The capacitor is a 3 wire (one each end, one in middle). Installed the cap in same orientation. Tried swapping the power leads (black/white), motor wouldnt turn (just a brief pulse, sounded like a 3 phase motor being single phased), switched them back.

The Cap is an exact replacement, but should I try putting the old one in? Motor-Emerson K55HXSSM-7146, Cap is a Cera-Mite 305CIS 5uf... Thanks

On 2018-07-26 by Kris

im having issues with my Bryant AC unit. It has a 2 stage compressor.

I noticed the air wasn't getting cold during the night and the next morning on the thermostat, noticed that there was message, System Malfunction, giving me a code of 76. Low Stage repeat. No Start. it provided. any ideas where to start?

On 2018-07-20 by (mod) -

There are some units designed to move air from the top down and out through two or three sides across the condensing coil.

But if your fan has actually reversed-direction, as is possible with some motors, it could have suffered a power surge or lightning strike. See

ELECTRIC MOTOR RUN DIRECTION https://inspectapedia.com/electric/Electric_Motor_Direction.php

On 2018-07-20 by Joan Nering

My AC is only blowing air. When I checked the condenser the fan is blowing downward instead of blowing up and out!

On 2018-07-10 by Barry

Condenser fan bows air out top of Carrier HVAC at 20 degree angle rather than straight up 90 degrees. Installed new fan but no improvement. Appears all hot air not being expelled so unit is not cooling like it used to. Runs constantly until evening. Suggestions on what to do to improve?

On 2018-06-14 by (mod) -

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

On 2018-06-13 by Anonymous

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?

On 2018-05-24 by (mod) -

No not at all, however cycling air compressor off and then back on to quickly can damage the compressor motor by forcing it to try to start against the high head pressure.

On 2018-05-24 by Jyoten

What happens if compressor is intentionally kept Off for a few minutes and the condenser fan is running for that time? Is it detrimental to the system ?

On 2018-05-17 by (mod) -

Check for

- a bad fan motor bearing

- a bad fan start capacitor

On 2018-05-17 by Sax

Condensing unit fan squeals before it's at full speed then runs great

On 2018-02-18 by (mod) -

The condenser unit cannot function and should shut down on over pressure or tempetature.

On 2018-02-17 by Will

What would happen if one of my condenser fan's stop runn5

On 2017-12-14 by (mod) -

Check first for a bad heater on the compressor

On 2017-12-13 by Mike

Yes I’m in Pa and it only happens during heat season. It started near the end of winter last year and it cooled all summer with no issues. As soon as we switched back to heat mode it started again

On 2017-12-13 by (mod) -

High amps usually means that a compressor motor is unable to start. If it's a heat pump and it's supposed to be able to run, resuming that you're in a cold-weather area and therefore are running the heat pump in heating mode, Maybe the compressor cannot start because the crankcase heater has failed

On 2017-12-13 04:27:15.390598 by Mike

Nordyne unit with IQ drive keeps throwing an “outside compressor rotation fault “ when on heat mode. Does this once or twice a day any thoughts? Also saw a “ high compressor amps” pop up

On 2017-12-11 by Jeff Maraman

The condenser fan for air should not run for the heat should it

On 2017-12-06 by (mod) -

I would look for a bad fan relay

On 2017-12-05 by Angela

I have a Coleman heat pump and have replaced the capacitor. The inside furnace will run and heat but the outside fan will not come on and the unit begins to freeze up, what could this be?

On 2017-10-24 by Frank

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.

On 2017-10-24 by (mod) -

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.

On 2017-10-23 by Frank

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?

On 2017-10-08 by Sandra

A couple times a day AC blows hot air into the house for about 5 to 10 minutes before kicking in cold air - is thiis normal? Brand new AC installedl Model # 4WCY5060A1000AB American Standard Packaged Heat Pump

On 2017-09-26 by (mod) -

Wanda

IF there is NO air output then I suspect there is a problem at the fan or blower unit. But if there is air output of air that is not cool enough, working on the fan itself shouldn't cause that problem - unless by accident hubby left a wire disconnected at a control relay or board.

On 2017-09-26 by Wanda

My husband replaced the fan blade on our ac unit because it was loose and making a lot of noise. Our ac has not put out cool air since he did this. Is it possible he caused other problems?

On 2017-09-25 by (mod) -

Sounds like a motor is overheating and shutting off on thermal reset.

On 2017-09-25 by Orlando Garza

Working on a Goodman heat pump unit 5 ton changed out the condenser fan motor capacitor and contactor it will run for 20 to 30 minutes then it stops running

On 2017-08-22 by (mod) -

Anon:

If a backwards running fan means that the proper CFM of air flow across a coil does not occur, in a CONDENSER in cooling mode (air conditioning mode if it's a heat pump) then the condenser will be too hot, the high pressure gas will not adequately cool to liquid form, but none of that would cause icing of the outdoor coil.

An indoor evaporator coil will freeze up if air flow is reduced or cut off for any reason: backwards fan or dirt or dirty filter.

On 2017-08-22 3 by (mod) -

Mohammad

I'd like to help but have no information about your system that would let much guessing make much sense. Perhaps your service tech will checkout the control modules or relays against what the manufacturer says should be happening.

On 2017-08-22 by Mohammad

I have single package air conditioner with two outdoor fan motors, motor 1 stops when motor 2 gets on . please advise

On 2017-08-08 by Anonymous

Can a condensor fan running backwards cause evap coil to freeze up

On 2017-07-09 by (mod) -

Ron

Which fan - outside compressor/condenser?
Anyway, look for

- shorted thermostat wires - disconnect them at the blower or compressor unit end

- a bad fan relay

On 2017-07-09 by Ron

Compressor contacts disingage and fan sill runs,disconnected thermostat and still runs,wont shut off unless pull disconnect

On 2017-07-05 by (mod) -

Good question. Im notsure of the cause but suspect

A bad thermostat

Loose or corroded wires or connection

A bad a.c. control or relay

On 2017-07-04 by Lynn

I have a new carrier 2 1/2 ton 83,000 but heat pump. When the ac is running and it reaches the temp on the thermostat, the cooling shuts off, then immediately restarts and runs for a few minutes, then stops again. What causes this?

On 2017-06-28 by Daniel

I need to know what the HP rating is on my condenser fan motor for a Bryant 3 ton 13seer model 564bnx036000

On 2017-06-28 14:36:57.576056 by Anonymous

Need to buy an air conditioner condenser fan motor for a Bryant outside unit anybody know where I can buy one

On 2017-06-18 by Ricky

Our condenser fan seems to just shut off- repairman says pressure lockout. He reset and checked the pressure After his service visit the fans stopped again. The fan starts working immediately after the slightest pressure on the housing ( leaning in to look in at the fan blades - has happened 3 times) Any idea what the problem might be?

On 2017-06-09 21:59:53.047198 by (mod) -

I don't think so, Ron, those sound like separate problems. However if there was an "event" like a lightning strike that might damage both the fan motor and the compressor motor.

Yes a mistake during work on any electrical equipment might accidentally touch a live electrical component to ground, causing damage or worse, a shock. But of course we can't know by a simple e-text what your contractor was doing nor if there was any possibility at all that she caused the trouble you describe.

On 2017-06-09 12:05:15.502447 by Ron

Question-Is it common to see compressor ground out after replacing condenser fan?
Carrier AC-Fan was making screeching sounds periodically, and also only operating at 70%, so had it replaced. Condenser also replaced. When tech installed new fan, it was confirmed by error code with Carrier, that compressor grounded out. Tech said that with the high amperage coming off new fan, compressor was used to the amps coming off old fan, and it grounded out because of this. I don't know a lot about AC units, and compressors, but could my contractor have caused the compressor to ground out?

On 2017-06-07 21:48:25.059455 by (mod) -

Jim,

With electrical power off if you are unable to rotate the fan at the compressor condenser unit then it sounds to me as if the motor bearing or motor itself has seized and the motor will need to be replaced

On 2017-06-07 18:46:49.578771 by Jim

My fan on AC unit will not spin tried by hand won't even move a bit I tried with both hands

On 2017-05-30 23:55:55.285176 by (mod) -

Thornton,

I don't know for sure. If the system starts and runs, you can run it. If the compressor or fan motor hums and doesn't start then you need to leave it shut OFF as that humming is drawing current that could damage the motor or its controls.

Rohit:

The fan for a split system A/C compressor - are we talking the indoor blower fan or the outdoor compressor condenser fan? Generally the best approach is to take a look at the data tag on your equipment or your owner's manual.

Armed with the brand, model, and serial number you can order the proper fan motor or whatever other parts you need, from the manufacturer or from an HVAC supplier. That'll fit more easily than guessing at reading fan motor specs and mounting specifications to install a generic part.

On 2017-05-30 19:06:06.655960 by Thornton

I know my dual capacitor needs to be replaced. Is it safe to run AC unit ,even for short periods, until I can get it done?

On 2017-05-27 10:36:01.212806 by Rohit Naik

pl inform from where could i get fan for my split AC Compressor...?

On 2017-05-27 10:33:15.143835 by Rohit Naik

What is reason behind compressor fan of AC which is breaking up again & again. Provide me proper solution

On 2017-05-24 19:07:29.207558 by (mod) -

Got it now Goeff

Let’s look again at the case where the outdoor compressor/condenser fan is cycling on and off at short intervals - in seconds:

The list of possible causes of an intermittent HVAC compressor/condenser fan operation when the compressor motor itself runs normally includes at least:

- a bad fan motor start/run capacitor

- usually easy to find and swap out for a new one so often the service tech will start by just replacing this part.

Often a tech will replace both the start/run capacitor AND the fan or condenser+fan relay since that can save the cost of a second service call.

These are not expensive parts. You can also find more about start/run capacitors at InspectApedia - CAPACITORS for HARD STARTING MOTORS

Watch out also that a remaining charge in a capacitor can shock you even if power is OFF - an expert will ground the capacitor terminals to dissipate any remaining charge. The capacitor specifications are printed on the device.

- a failing fan motor that's overheating - when the power is turned off after the system is on for a while see if the motor feels very hot - some motors include an internal thermal reset - this is of course a more expensive part to swap in so try the capacitor first.

- a bad fan control relay in the compressor/condenser unit. If the fan cycling were running at odd times/intervals I'd suspect a bad connection or loose wire but if it's regular cycling on and off more likely it's a control problem (or overheating)

- less common: a fan motor winding that opens when the motor gets up to full speed

- other electric motor defects cited at the motor diagnostic article series

see ELECTRIC MOTOR DIAGNOSTIC GUIDE and in that article series

we also have an article on ELECTRIC MOTOR RESET BUTTON


WATCH OUT: there are very serious hazards when fooling around with the compressor/condenser unit including death by electric shock or having fingers chopped off in a spinning fan. If you’re not trained/qualified to do this repair work it’s best to hire a trained service technician. In any event be sure power is off before getting closer into inspection of the equipment.

On 2017-05-24 by geoff

Yes great customer service! I was surprised no technical help. It is just the fan on the outdoor unit thats cycling 3 seconds on, 8 - 10 seconds off.

The compressor was running steady during the cycling of the fan. Let you know what i come up with,
Thanks

On 2017-05-24 by (mod) -

Geoff

Wonderful. What a perfect short-term-bottom-line grab the money and run business strategy that you describe about 8 Payne Heating & Cooling S 7310 W. Morris St. S Indianapolis, IN 46231. Putting the customer last is a good way to wipe out your business.

The company's customer contact number (888) 417-2963 is probably what you called. What you report is disappointing for a company that's been around since 1914. At the company's website https://www.payne.com I also did not find more technical support information.

A sample Payne owner's manual http://www.utcccs-cdn.com/hvac/docs/1009/Public/0E/OG-PAYACR410-01.pdf offers 2 pages of general operating instructions and no troubleshooting advice.

What's left is to call the service manager at your local HVAC repair company and ask for a more-experienced service technician. But first read the SHORT CYCLING AC COMPRESSOR article so you're familiar with the terms and common causes of the trouble.

To be more clear: is it only the fan motor that's short cycling or is the compressor itself cycling on and off rapidly?

I'd also check again for a loose wire or other electrical component like a relay or board connector.

On 2017-05-24 07:41:12.407022 by Geoff

,
Thanks for the link and your comments. I called the customer contact # at payne and they do not have anyone that answers technical support questions. They said talk to the retailer. That go me nowhere.

This is brand new unit and was fired up for the 1st time and was intermittent fan. The condenser is running fine and it seems to cool the house, issue is with the fan. I found some info saying depending on the outdoor temperature, the fan will cycle on and off, more so on when its a hot day outside and less when its cooler out.

They said it possibly has a "head pressure control" allowing it to run in low temps. Someone also suggested a faulty defrost sensor.

I only ran the unit for 15 minutes , but wanted to do more research on the intermittent fan before running longer. I will run it for longer tomorrow, Its supposed to be fairly warm outside so will see if the fans runs in longer cycles.

On 2017-05-23 23:35:59.266981 by (mod) -

Geoff

I don't pretend I know more than a full time HVAC expert technician, but gee: it really sounds abnormal me for a compressor to continuously short cycle on and off every 10 seconds and I'd expect that cycling to ultimately damage a control, relay, or the compresor itself. It's enough of a problem that we have an article on it

SHORT CYCLING AC COMPRESSOR at https://inspectapedia.com/aircond/Air_Conditioner_Short_Cycling.php

I worry when encountering what sounds like baloney that someone is just brushing us off, figuring that when the system dies they'll sell us a new one.

Call the service department, ask to speak not to a sales rep but to an experienced service manager. Politely ask that they send a more experienced tech to look at the problem.

Keep me posted as what you're told will help others.

On 2017-05-23 18:47:19.568993 by Geoff

, the salesperson assured me that this was normal to keep the pressure high? I don't think its how it's supposed to be though?

On 2017-05-22 21:43:12.394263 by (mod) -

Geoff

That sounds like a bad control board or relay, or perhaps a loose connection. I'd think that if the problem were a motor overheating the motor would stay off longer than 10 seconds.

On 2017-05-22 21:25:02.956871 by Geoff

I have a brand new payne outdoor ac unit. The condenser fan runs intermittently. Runs for about 3 seconds then off for about 10 seconds . And does that continuously . Is that normal? Any info would be appreciated.

On 2017-05-10 14:44:12.372723 by (mod) -

AirSpeed can vary considerably in a residential low pressure HVAC duct depending on system design. The speed ranges from about 175 cubic feet per minute to 5900 cubic feet per minute. Most likely you'll be in the low end of that range.

On 2017-05-10 07:05:38.666656 by Sagar Lokare

what would be the speed of the air that takes away the heat from the refrigerant in the condenser?

On 2017-04-14 22:57:10.566120 by (mod) -

I suspect that the technician installed a "hard start" capacitor because the standard cap was having trouble starting the motor.

On 2017-04-14 16:03:57.305894 by eddieo

I just would like to know the reason somebody instead of just change the bad capacitor. He installed an emergency capacitor?


...

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