# Goodman 2 stage 80% Furnace(GMH80603ANBB) Intermittant 24VAC to Low Heat valve solenoid



## VBJMalley (Jan 13, 2021)

Good Morning all. Joe here from Virginia Beach.

My step daughter's furnace, model in the title, intermittantly fires up. When it fails, no 24 vac to the low heat solenoid on the honeywell dual stage gas valve. When I traced the circuit I moved the wire close to the ICB and it immediately fired.

The Control board in the furnace is a PCBBF132. Goodman docs call for a White-Rodgers 50M56 ICM for the GMH model. The furnace is set to single stage only. In that setting the low heat valve must open and then the Hi heat valve. The Aux. Limit switch is in series with the voltage supply to the valve.

I am thinking either a cold solder joint on the baord, loose wire/pin on the harness or an intermittant limit switch.
It has run fine all week until this morning. I ordered the board, the limit switch and harness(just-in-case)

Could it be possible the Blower housing getting too hot and activating the limit switch causing the intermittant operation?

Any feedback appreciated. Something I may be missing ?

In addition, the furnace goes through the power up sequence to the ignitor glowing every time. I checked the valve by applying 24 VAC power to the low heat solenoid and opens correctly.


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