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 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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HVAC Compressor/Condenser Fan Motor or Start Capcitor 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

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Condenser Fan Motor or Fan Motor Capacitor Failure FAQs

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: condensor will start but slow to start

My condensor trys 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 squelling 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 intalled 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 reparied. 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.

 

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