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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14007
Experience:  15yrs in the HVAC industry with certificates and degrees.
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The air handler fan motor on the heat pump air conditioning

Customer Question

Hello. The air handler fan motor on the heat pump air conditioning unit keeps randomly cycling on and off like the motor is trying to start. I replaced the motor start capacitor.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yes
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: I notice that if I switch the fan setting from on to automatic, this will stop the random cycling.
Submitted: 4 months ago.
Category: HVAC
Expert:  HVAC Guru replied 4 months ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset. I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. I just picked up your question now. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly I am not paid anything until you rate my service good using the STAR RATING LINK at the top of your page, the money is paid to the site not me directly.

Answer:

Check the low voltage wiring at the contactor and connections out at the unit, if you have a bad low voltage connection that will keep dropping out the contactor causing that issue. Often a thermostat wire that is wire nutted is the issue as the connections go bad.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

Customer: replied 4 months ago.
I'm using a Honeywell RTH9580 WiFi smart thermostat. I also noticed that when this motor cycling occurs, If I just remove the thermostat From its base on the wall, the cycling stops.
Customer: replied 4 months ago.
the fan motor runs normally in scavenge mode until the timer in the air handler times out.
Customer: replied 4 months ago.
The air handler is a Trane Model TWE042C140C0.
Expert:  HVAC Guru replied 4 months ago.

Oh Ok you likely have the pin base correct where the thermostat has pis that go into the base plate to make connection correct?

Customer: replied 4 months ago.
Do you know where the control circuit board is on this unit
Customer: replied 4 months ago.
Correct.
Expert:  HVAC Guru replied 4 months ago.

Lets start by the thermostat please remove it and do this....Find the RED and YELLOW wires there do you see them?

Customer: replied 4 months ago.
Expert:  HVAC Guru replied 4 months ago.

OK can you connect those two wires together and see if the AC comes on and runs fine without issue?

Customer: replied 4 months ago.
It will take a while to tell. Sometimes this only happens after hours of operation.
Customer: replied 4 months ago.
again, with the thermostat removed, the fan motor is running normally in scavenge mode right now.
Expert:  HVAC Guru replied 4 months ago.

No problem....do that and see or clean off the base connections and using an eyeglass screw driver after cleaning the connections off carefully bend the tabs so they grab the pins tighter and try it. Often that base is the issue and the pins lose connection with it causing that issue.

Customer: replied 4 months ago.
I will try that and get back to you later in the day. Thank you.
Expert:  HVAC Guru replied 4 months ago.

OK great! If i am away I will get to it as soon as I am around...I have some stuff to take care of later but I will be back at some point

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!