I have a 2002? Goodman Gas Furnace, model:GMNT120-5
The blower (fan) runs constantly, even if the t-stat is off/heat/cool
or is set to on/auto.
I pulled the cover and everything appears fine, nothing burnt or
damaged, the cabnit is clean. Fuse is good, and the trouble shoot LED
is on indicating normal operation(per the manual).
To rule out a short in the Green 24v wire I unhooked it and swapped out
a with another and the fan still comes on.
Sitting in front of the control pannel with everything hooked up and
power on.. I can press the door switch and the LED will light up and
the cap will begin to energize, when the cap is energized the relay
will trip and the fan will come on. If I unhook the green(fan) wire
this doesn't happen.
I've changed the t-stat (wanted a new programable anyway, so that's
ruled out also).
Also wanted to say that the heat does work, if I dial the t-stat above
room temp and set the t-stat to heat, the burner lights and heats the
house to temp, then shuts off(but the fan stays on).
At this point I'm guessing a new control board?
Thanks for any help.
Lift 24 volt red from the board, press the switch. If the fan still comes
on, check the motor leads to the board, make sure you don't have a board
with a port for continuous fan. You should have one motor lead to common
(white), one to the heat port and one to the cool port. If the fan still
runs, you probably have a bad board or a shorted wire between the motor
leads and something else.
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