Weird Goodman furnace problem

Old 01-24-15, 07:33 AM
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Weird Goodman furnace problem

Hi there! I have a 19 year old Goodman GMP075-3 furnace. The problem I am finding is quite weird and not really sure what could be wrong.

The furnace stops working after reaching the set temperature. For example if I set the house to 22 celcius and it reaches 22 and after that the furnace will not turn back on and temperature just keeps dropping obviously without the furnace ever kicking in. So if i set the temperature to below existing temperature in the house (for example I bump it down to 18 wait 10 seconds and then bump it back up to 22) or if I turn off the power to the furnace and turn back on, the furnace starts heating as normal.

Any ideas?
Old 01-24-15, 07:52 AM
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Welcome to the forums.

Go to your furnace..... see if you have a small round glass in the blower door. That should allow you to see the furnace control board. You can also remove the blower door now to familiarize your self with the board location. If you have the door off you need to hold the safety switch in. Once the furnace is active, don't remove the door as that will turn off the power and clear the flashing code.

What we are trying to do is to see if it's a thermostat or furnace problem. So allow your house to come up to heat and shut off without touching thermostat. If the temp drops and the furnace doesn't fire..... check the flashing red LED. Note the pattern. The flash patterns are actual printed on the back of the blower door.

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