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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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The blower motor continues to run, with the thermostat set

Customer Question

The blower motor continues to run, with the thermostat set on auto and when compressor shuts down. I replaced the fan motor relay, and still no change.
Submitted: 1 year ago.
Category: HVAC
Expert:  HVAC Guru replied 1 year 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.

If you disconnect the thermostat wires from the board does it stop running?

Customer: replied 1 year ago.
This unit is before circuit boards. I have a Airtemp unit from appx. 1984 to 1986, it has a motor relay. I did remove the wire from the thermostat to the relay and blower continued to run. I also removed the wire from cooling condenser with the same results. I did replace the relay with a new one still with no change.
Expert:  HVAC Guru replied 1 year ago.

So it is just a really by itself not on a board correct do you have a picture of it?

Customer: replied 1 year ago.
Sorry no schematics or pictures, the unit consist of a thermostat, low voltage transformer, gas control valve, heater temperature control switch/limit switch, and a blower motor relay.
Expert:  HVAC Guru replied 1 year ago.

Let me see if another expert has an idea

Expert:  bonzaco replied 1 year ago.

Hi my name is ***** ***** can you tell me what controls the relay?

Customer: replied 1 year ago.
I am guessing that a signal from the thermostat.
Expert:  bonzaco replied 1 year ago.

OK where does the motor control relay receive its switching power from?