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I am trying to troubleshoot what is causing my blower to run non stop (the condenser (outside unit) comes on only when cool is required). There is no issue with cooling the house. I read through all the posts related to similar issue from this forum, but my issue looks peculiar. I checked the thermostat, the fan is set to auto and the wirings look good. Upon testing the control board with a multimeter, the HI HEAT terminal is showing 120 volts even when the thermostats are off or removed. I checked the limit switches and they are showing 0 volts, so they are not tripped either.

For now, I have detached the wire from the HI-HEAT terminal (that goes from the terminal to blower) and the unit is tuning on and off along with the condenser unit (only when the cool is required). However, summer getting over, I want to get this fixed before the winter cold starts.

I think it is time to check with our experts on what is causing the HI HEAT terminal to request 120 volts which in turn is making the blower to run non stop.

The unit is a Goodman GME80805DXAA attached is the wiring diagram. GME8 Wiring diagram

  • Try turning off the unit at the local mains disconnect (or circuit breaker), disconnecting the incoming black wire from the LINE-H terminal on the control board, then taking an ohms measurement from LINE-H to HI HEAT-H using your meter, and posting here with the answer. – ThreePhaseEel Sep 21 '19 at 3:01
  • Thanks for the directions. I followed them and the meter is reading 0 ohms and beeps to denote continuity. Why would this happen? Is the board faulty or is there any short in the circuit? – Bob Sep 21 '19 at 17:11
  • Interestingly. I put the furnace covers back and turned it ON. The blower started to run non stop after even with the HI HEAT wire unplugged. I tested the control board and now the COOL terminal was getting 120 volts even after the thermostat was turned off (similar to what the HI HEAT terminal was doing previously). I gently tapped the control board and voila the fan stopped. I quickly tested the board and there was no voltage to COOL terminal (the thermostat was still turned off). But the HI HEAT was getting 120 volts. Is this a result of a faulty board or something else? – Bob Sep 21 '19 at 17:46
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Yeah, your control board is shot

I'd replace the control board if I was in your shoes; the behavior you are seeing is a sign that the relays on the board that control the blower motor are failing, or something is causing it to drive them uncommandedly for that matter.

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  • Thanks. Ordered one on Amazon. Hoping that swapping the board will fix the issue. Anything to be taken care of while changing the board? amazon.com/gp/product/B00Y1PVGLW – Bob Sep 22 '19 at 0:49
  • Thank you. I replaced the board today and the blower is working good. It is turning on and off along with the condenser outside. Very much relieved that it is working good. However, still wondering what could have made the old board to work weird and a bit afraid if the new board will result in a similar shot. The unit is 5 years old and I am not sure if a board could go bad in 5 years. – Bob Sep 23 '19 at 4:04
  • @Bob -- check the old board for signs of damage. (been there, done that) – ThreePhaseEel Sep 23 '19 at 11:41
  • Also, we say "thank you" around here by upvoting and accepting folks' answers :) – ThreePhaseEel Sep 23 '19 at 11:42
  • Oh yea. I did upvote, but got an error message as "Thanks for the feedback! Votes cast by those with less than 15 reputation are recorded, but do not change the publicly displayed post score." :) – Bob Sep 24 '19 at 16:52

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