y HVAC Compressor / Condenser Fan FAQs Set #2
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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 2

Q&A to Diagnose & Fix the outdoor unit fan, motor, or start capacitor

A/C or Heat Pump Fan Condenser Unit Fan diagnostic questions & answers, set #2, about the outdoor compressor/condenser unit fan, fan motor, or the condenser fan motor start capacitor.

This article series 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?

HVAC Compressor/Condenser Fan Motor or Start Capacitor FAQs

Air conditioning compressors overgrown with shrubs (C) Daniel Friedman

These questions and answers about the outdoor unit fan operation were posted originally

at FAN, COMPRESSOR / CONDENSER UNIT - be sure to see the diagnosis and 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.

Article Contents

...

Condenser Fan Motor or Fan Motor Capacitor Failure FAQs

Also see our capacitor diagnosis and repair guides beginning

at CAPACITOR TYPES, for MOTORS

How do I figure out the replacement for my old AC Compressor Capacitor?

Old AC compressore capacitor terminals compared with new ones (C) InspectApedia.com StephenRetail

Retail Stephen

Wondering if anyone can figure out the replacement for my old ac capacitor. The newer says HCF (Herm, common" Fan) but based on the wiring diagram it shows BCA. Please help!! Please see pictures attached - 2022/08/18

Old AC compressore capacitor terminals compared with new ones (C) InspectApedia.com StephenRetail

Moderator reply:

Sure - the values are right on the cap, but you can also follow the steps at

CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

or if you need help wiring it up

MOTOR CAPACITOR WIRING GUIDE

You'll see that it's pretty straight forward: 3 wires, Common, Fan, & Compressor.

Old AC compressore capacitor terminals compared with new ones (C) InspectApedia.com StephenRetail

 

 

Can a fan itself on a heat pump be bad?

Can a fan itself on a heat pump be bad

Reply: yes:

Yes, Including

A bad fan motor

Bad start run capacitor

Damaged fan blades

Fan loose on motor shaft

Loose motor mounts

Bad fan relay

 

Question: outdoor fan for the condenser/compressor stopped but can kickstart it with a stick

Trying to diagnose my problem. My outdoor fan for the condenser/compressor stopped. I am able to kickstart it with a stick. Once running by this method, however, the unit does not seem to be cooling.

The first thought is I need a new capacitor, but since after doing the kickstart, I don't get cold air coming out the vents (my blower is running), is there something else I should be checking or is it probably still a capacitor issue? 2017-07-13 by Michael

Reply:

Michael:

The first part of the question sounds as if the fan has a bad start/run capacitor.

But your second concern could be

- the fan never runs fast enough to cool the hot high pressure gas back to a liquid refrigerant

- there is a refrigerant leak and lost refrigerant

- the compressor is not starting at all

- another defect like a bad expansion valve is not permitting refrigerant to be metered into the cooling coil

 

Question: condenser will start but slow to start

My condenser tries to start at sometimes it will start but slow to start. When it wont start I can spin it with a stick and it usually starts. After it runs a little while it shuts down. 2017-05-10 by tom

Reply:

Most often the problem you described is caused by a bad start capacitor for the fan motor. The service tech typically just changes that part to see if it fixes the trouble.


Question: compressor fan comes on, runs slow, then stops turning

outside compressor fan comes on runs slow then stops turning and unit starts making a humming or squealing sound. 2017-05-08 by Mark L Tucker

Reply:

Sounds like a bad fan motor start/run capacitor or perhaps (less likely) a bad control board.

 

Why the technician installed an "emergency" capacitor

I just would like to know the reason somebody instead of just change the bad capacitor. He installed an emergency capacitor? 2017-04-14 by eddieo

Reply:

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

 

Short life of replacement capacitor

Condenser fan wasn't running. Read out the motor, Appeared good, replaced the run capacitor, came back to life for 8 hours and the fan stopped again. Any ideas? 2016-06-24 by jesterdan

Reply:

If the replacement cap didn't give more than 8 hours of running I suspect that the motor is failing; keep in mind that some motor problems such as a winding that opens when the motor is spinning, can be hard to find. Search InspectApedia.com for ELECTRIC MOTOR TEST to see some diagnostics.


Old Williams AC unit's fan shut off but compressor kept running

Hi I have an old Williams AC unit Has been working fine for about 15-20 Years.

When I started the AC this Year, the outside unit Fan and compressor started up OK then after 20-30 seconds the fan shut off while compressor kept running.

Then the fan started again for some seconds and quit it just kept cycling. It is a 220 fan motor and the voltage stayed constant on my Simpson. What can I do? 2016-06-15 by Jay

Reply: check the fan motor and capacitor

Check for a loose connection or a bad start/run capacitor.

Keep in mind it could be a bad or failing fan motor itself.

Follow up:

connections look OK nothing loose & full voltage all the time, how can I check the start /run Capacitor?

Reply: how to test the motor capacitor

https://inspectapedia.com/electric/Motor_Capacitor_Tests.php

Follow up:

Thanks for the help Danjoefriedman, Must be the motor itself, Think I'll just replace both and see if that fixes it.

Cap seems to be OK too, On high scale of the simpson (100000ohm) get full deflection then infinitive. When I reverse the leads it is the same, no short to case. Don't see much on the 10K scale.

Reply:

Jay often we'll test the motor out of the unit by wiring it directly; even before doing that, if the motor shaft doesn't turn easily that's an indicator of a mechanical problem; electrical motor problems can be subtle as a winding may only open when a motor spins.

Search InspectApedia for ELECTRIC MOTOR TESTING to see more suggestions if you like. DO keep me posted.

Daniel

Follow up: success replacing fan motor

Thanks again for the help Daniel, That is exactly what I did Today and after cleaning and lubricating the old motor it still cut out after a while just took longer. Went to the supply house and got a new motor. I test ran it out of the unit and no more cycling.

Must have had a shorted or open turn which caused the old motor to overheat or open up. End of story, I am ready for hot weather, maybe I get another 10 Years out of it!

Reply:

Nice going, Jay.

 

A/C unit on the outside fan starts spinning and about 1 min later it slows down

When I turn my a/c unit on the outside fan starts spinning and about 1 min later it slows down and like 10 seconds later it cuts back on running the way it should. it did it off and on. the air inside never gets cool enough to cool the place down. 2015-12-07 by keith H

Reply:

Keith

The problem may be a start-run capacitor on the fan motor, or a bad control or relay.

Search InspectApedia.com for STARTING CAPACITOR to read details.

 

Breaker is tripped - The fan motor is now probably shot

The fan outside our unit has quit running a month before I heard a little hum for a few seconds every once in awhile now that breaker is tripped we put it back on and it tripped the breaker again so now the breaker is off the heat works fine but the blade is not turning outside could you help me with that please. 2016-03-01 by cathy

Reply:

The fan motor is now probably shot - or its start/run capacitor is shot. Leave it switched off until that's repaired. Meanwhile you're on backup heat.

 

Condenser Fan motor in outside unit went bad - replacement affected cooling?

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.


Fan motor shaft moves up and down

My condenser fan motor shaft has up and down play but the amp draw is good. Is the fan motor still bad? 2016-03-06 by Kevin

Reply:

Kevin

I'm not sure what's moving up and down - that is, if the shaft wiggles from side to side when moved against the motor bearing I suggest the bearing has failed.

But end play described as a movement of the motor shaft in and out - say by pushing or pulling on the end of the shaft so that you are pushing it into our pulling it out of the motor, as opposed to side to side against its bearings - that may be OK.

 

Reader question: My AC is only blowing air

My AC is only blowing air. When I checked the condenser the fan is blowing downward instead of blowing up and out! 2018-07-20 by Joan Nering

Mod reply:

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

 

Reader question: outside compressor rotation fault and high compressor amps

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. 2017-12-13 by Mike

Mod reply:

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.

Follow up:

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.

Mod reply:

Check first for a bad heater on the compressor

 

Reader question: fan on AC unit will not spin

My fan on AC unit will not spin tried by hand won't even move a bit I tried with both hands. 2017-06-07 by Jim

Mod reply:

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.

 

Reader question: condenser fan runs intermittently

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. 2017-05-22 by Geoff

Mod reply:

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.

Follow up:

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?

Mod reply:

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 compressor 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.

Follow up:

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.

Mod reply:

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.

Follow up:

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.

Mod reply:

Got it now, Geoff.

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.

 

Reader question: confusion when new capacitor has different number of connectors or wires

My condenser fan went out it has 4 wires i bought a new fan and it came with a new single phase capacitor my unit has a dual capacitor ...and colors of wires are different but new fan has plug ins for capacitor ..can i get some help please. 2019-05-02 by Matt

Moderator reply:

Matt.

Please try the search box at page top or bottom find our article on CAPACITOR WIRING

there you'll also find CAPACITORS SELECTION to be sure you have bought the proper type of cap.

 

Question: stored energy in the capacitor is discharging into the compressor?

They are here now to fix it. What they are going to try first is replace the Board since it's easier/cheaper. They say the stored energy in the capacitor is discharging into the compressor and the fan on shut down. We'll see...

They changed the board but it still doing the same thing. They are going to replace the compressor next week. The system is running on emergency heat so the whole thing doesn't burn out in the meantime. They have never seen this problem before which is a little surprising since it's a company with 5 locations, not a mom & pop business. 2018-01-17 by Mark

Reply:

Mark

Thanks for the updates. All of this sounds strange to me but probably we're seeing a communications gap between the technicians and the rest of us. There sounds like a confusion between volts and amps, or at the least, I'm unclear how a control board OR a bad compressor would change the VOLTAGE readings.

Central air conditioner compressors run at 120VAC or more-often 220 or 240 VAC nominal voltage.
Some units will specify an acceptable range such as 208-230VAC or, depending on your country and electrical service, up to 250VAC.

I agree that 246VAC is within acceptable limits for the supply voltage to many AC condenser units.

The AC circuit should be dedicated - it should not be also supporting other electrical equipment.

If the supply voltage (from the electrical utility) is exceeding what the equipment can handle that can damage the equipment. But you'd want to do more than just fix the equipment; you'd probably want surge protection and voltage conditioning equipment to protect the repaired compressor/condenser unit from new damage.

A typical voltage stabilizer will handle voltages ranging from 170-270VAC and will keep that voltage in the range needed by your equipment.

Research:

Ortega, JM Maza, M. Burgos Payán, JM Romero Gordón, and M. Pinilla Rodríguez. "Supply Voltage Effects on the Operation of Residential Air Conditioning Appliances: Theoretical Analysis."

Follow up:

Well, they replaced the compressor and it is fixed now except we won't know why is was doing that. All they could say was the capacitor was bleeding into the windings. Since it is under warranty it will go straight back to Rheem so no finding out what this phenomenon was except that it can happen.
Thanks so much for your time and attention, though.
Best Regards,
Mark

Reply:

Capacitor bleed into windings is not quite a diagnosis I understand but I infer that the start or run capacitor was defective.

 

Reader question: Is it safe to run AC unit, even for short periods, until capacitor replaced?

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? 2017-05-30 by Thornton

Mod reply:

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.

 

...

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