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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. Heat Pump Compressor / Condenser Fan FAQs #5
Recent Q&A on Diagnosing the Outdoor AC unit fan operation

A/C or Heat Pump Fan Condenser Unit Fan diagnostic FAQs No. 4.

These questions & answers about the outdoor unit fan opeeration help diagnose problems with the air conditioner or heat pump condenser unit fan or with no-cooling or no heat (from a heat pump) system.

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

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

HVAC Compressor/Condenser Fan Diagnostic questions & answers

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.

If you are troubleshooting the indoor air handler blower fan that delivers cooled or heated air through the duct system and supply registers, see BLOWER FAN OPERATION & TESTING - home.

On 2019-07-06 by (mod) - outdoor A/C compressor unit overheat & shut down because fan running backwards

HM

Thanks so much.

Your follow-up about diagnosing the A/C condenser fan will certainly help other readers.

An on-site expert will always be smarter than a guy sitting at a computer pecking at the keys down in Mexico.

The next time we read of a unit shutting down on thermal overload we'll be sure to add "is the cooling fan even running in the right direction?" diagnostic question.

BTW some motors can reverse direction following a power surge or lightning strike and will keep running backwards thereafter.

On 2019-07-06 by HM

I wanted to share this for everyone else's benefit and thank Dan Friedman for his input.

I brought a second HVAC tech out regarding the unit that would keep shutting down after 10-15 minutes and to safely check the operating voltage. He noticed immediately that the fan motor was wired in the reverse direction and corrected that along with using a gauge to adjust the pitch of the blades on the fan that were bent from running the wrong direction.

This created a situation where it was not dissipating the heat from the compressor but forcing the unit to work harder fighting against it. This is what kept engaging the thermal overload protection in the fan to shut it down.

The running amps (11) for the unit are now higher (18) and past the top end of the acceptable manufacturer operating range. This already aged system will fail and need to be replaced, I was hoping to limp it along another year in the AZ heat. That is now highly unrealistic.

The lesson learned is to THOROUGHLY review the tech/company that proposes to do the work. I was too focused on the overall savings and chose one vendor over another based on the quote. Cheaper is not always better, and I failed to do my due diligence using an HVAC "tech" over a solid company with properly trained and licensed technicians.

My system needed to be replaced regardless, but the potential damage could have been much worse given the electrical loads involved with the HVAC components. The risk is not worth it, and I am thankful for Dan and this website, providing the option to get an outside opinion for troubleshooting.

On 2019-07-03 by Anonymous

Thank you for your help.

On 2019-07-03 by (mod) -

Check first for a seized motor, followed by a bad relay and or a loose or bad wire or connector.

On 2019-06-29 by (mod) -

It's a certainly a reasonable speculation. Lots of motors have thermal overload safety controls built into the motor.
You might also want to check the voltage that's being delivered in the current being drawn. Beware if you don't know how to do those tests safely you could be shocked or killed.

On 2019-06-29 by HM

Replaced my condensing unit fan motor which sounded bad, very noisy like bearings failing and it started to cut out after 10-15 minutes of operation.
Also replaced the capacitors on condensing unit and up in the air handler. Cleaned the condensing unit coils extensively. The system worked normally for about 2 weeks, then it has started the cutting-out symptom again after 10-15 minutes.

When this happens the blower motor for the air handler is running normally, but not the new fan motor out in the condensing unit.

The relay looks too nice to be original, it looks new so I am assuming it has been replaced. I noticed if I let the unit sit for 1-2 hours after cutting out, it will start again and run almost every time throughout the night and cool normally. I was wondering if the new motor is overheating, and there is some type of safety that causes it to shut down to prevent damage?

The A/C is a 4 ton heat-pump, that is original contractor build grade Carrier brand unit which is now 14 years old, the tag is too sun-faded to pull an ID number. I am open to any feedback on this.

Thank you

On 2019-06-24 by CJ

Replaced fan and dual capacitor both are new but my fan still won't turn on. It's a heat pump is there a time delay for the fan? Or what else do you guys think it might be.

On 2019-06-23 by (mod) -

Sounds like a bad wiring connection or a bad fan relay

On 2019-06-2 by John Johnson

Carrier 38TKB030300 condenser fan was making noise - eventually quit. I assume the bearings seized and unit stopped. I replaced the fan motor and the capacitor. Motor still does not start. Compressor seems to work fine - coils heat up and you can hear the compressor running, but no fan.

On 2019-06-11 by (mod) -

Air conditioning and heat pump systems will in fact stop periodically to go through a defrost cycle.

On 2019-06-10 by Arturo

Does the Outside condensor fan stop running when thermostat is set to cool

On 2019-06-09 by (mod) -

Quite possibly or a bad starter relay or bad electrical connection or low voltage

On 2019-06-04 by Caleb

My condenser fan will run for a few hours and then stop. It runs and starts intermittently. When it stops there is a buzzing noise coming from the unit. The capacitor has been changed. Does this mean the motor is bad?

On 2019-05-16 by Karen

I have a heat pump and sometimes when I turn the furnace on, the heat pump fan won't start up and other times it starts right up when, why?

On 2019-02-10 by (mod) -

Chad

Please check the diagnostics starting

at FAN, COMPRESSOR / CONDENSER UNIT https://inspectapedia.com/aircond/HVAC_Condenser_Fan.php

or try

at FAN NOISES HVAC https://inspectapedia.com/noise_diagnosis/HVAC_Noise_Diagnosis.php#Fan

And let me know what success you have

On 2019-02-10 by Chad

My condenser fan makes a noise. Sounds like a air compressor. If I bump it the sound stops but returns next cycle. Everything seems tight. There is some play in the motor shaft but not a lot. Does this sound like the motor or blades?

On 2018-11-18 by (mod) -

That msy be normal. Eg. The fan stops during defrost cycke.

On 2018-11-15 by Andres

the outside unit fan motor suddenly stop after 5 o 10 min sometimes even doesn't start on heat mode (heat pump) when the temperature outside is cold (I would say below 55F).

On 2018-09-20 by (mod) -

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

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?

On 2018-09-20 by Carolyn reese

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 2019-06-10 by (mod) -

Sounds like a bad fan start/run capacitor or possibly bad fan motor.

On 2019-06-0 by VICKI

turn the a/c on and the outside fan starts then stop and then a few seconds later starts again and stops. moved everything away from it and i dont see anything in the fans

On 2019-06-07 by (mod) -

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.

On 2019-06-06 by Joe

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.

On 2019-06-06 by (mod) -

Possibky but the stsrt / run capacitor is the place to start

On 2019-06-06 by Sam

My fan won't turn on, but when I push it with a stick, it will. However, it will stop again a few minutes later. No noticeably colder air is coming through the vents at that time it is running. Do you think it is more than just the capacitor at fault? Thank you.

On 2019-06-06 by (mod) -

From what you described I suspect that the motor needs to be replaced

On 2019-06-05 by Todd

Hello and thank you for the information. I can't physically turn my motor on my heat pump last year a service tech told me there was some surface rust on the stator he was able to break free I was not there to see him do it. Does this sound like the likeli problem again? I didn't want to put too much pressure on it for fear I might damage or break the motor itself.

On 2019-05-02 by (mod) -

Matt.

Please try tne search box just above fo find our article on CAPACITOR WIRING

there you'll also find CAPACITORS SELECTION


On 2019-05-02 by Matt

My condensor fan went out it has 4 wires i bought a new fan and it came with a new single phase capicitor my unit has a dual capicitor ...and colors of wires are different but new fan has plug ins for capicitor ..can i get some help please

On 2019-04-23 by (mod) -

I guess if a thorough review of all of the connectors does not find a loose or corroded connection and we are looking at a bad control board or relay

On 2019-04-2 by Anonymous

@hey,

it could be over heating. But, i can reset everything. And wait. It might come back on in 5 minutes. Or it might not come back on in 7 days. it does not matter if the unit has been setting for many days after shutting off. For example it shut off about 5 days ago. I reset everything that I could reset. circut breaker etc.

And it came back on 1 day ago. it was about 60 degrees outside and 73 degrees inside. it just came on. It can do that when it is very hot outside or cold. It will run fine even on pleasant days. But it will just shut off. And it might not start running, the fan running and everything, for 1 to 14 days. it is as if it has a mind of its own. I have called people out to check on it. And nothing. it works. Then does the same thing. it has been happening for years now.

On 2019-04-20 by (mod) -

Hey Hey, I"m just guessing but if the compressor motor (or fan motor) is overheating it may be shutting down on thermal overload; when the motor cools off it will re-start.

It's time to ask for some diagnostic help from a trained service tech; she might include measuring the current draw of the motors for signs of excessive draw - a sign of a failing motor or bearing (or other problems), as well as checking for a sticking refrigerant metering valve and high head pressures.

On 2019-04-20 by hey

our fairly new heat pump will turn on and run well for 5 hours. Then it will shut off and not do anything. If kept off or on for several days, it will come on without notice or necessary need. It has been doing that for 7 years. always think it is broke, but it will start working for 5 hours or a month. then it will shuyt of for maybe 3 or 7 days and do it again. have had havc people check it. nothing fixes it

On 2018-08-08 by (mod) -

Paul,

The delay you described could be normal. For example in my office where we use a Sanyo split system air conditioner, the indoor blower unit may keep running at low speed but the outdoor compressor will turn on and off depending on when the control board (with its own computer) figures that it's needed. That's an energy-saving feature.

But IF your AC blower is delivering warm air AND the room temperature is still above the thermostat setting, then yeah something's wrong, perhaps with a sensor or control relay on the unit. That may not be a major repair cost ( a new compressor would be a major cost).

IF you hear the compressor humming but not starting, that's not very good and means there's a more serious problem. Call your service tech. Let me know what you're told.

On 2018-08-08 by Paul

Howdy, im no HVAC expert but i understand how it all works. My problem is that the indoor blower comes on, the outdoor fan comes on, but the compressor seems to take a while to come on, sometimes up to 10 minutes, meanwhile its blowing non cold air around the house.

I go outside next to the compressor, when it comes on i hear the fan but not the compressor (no buzzing sound), but it does come on later and then the freon pipe gets cold and im all good. I am in Miami and it is getting pretty hot here this summer, is this delay normal ? or is it a prelude to a more major issue ?

Thanks.


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