Goodman Furnace. No light on the circuit board


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Old 10-30-15, 03:51 PM
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Goodman Furnace. No light on the circuit board

I have a Goodman furnace and is not turning on when I turn on the heat on the thermostat. I started with the thermostat. Jumped the R and W on the thermostat nothing kicked on at the furnace. Next, I checked the on/off switch. All good, 120V. I then checked the junction box on the furnace. All good, 120V. I then checked the cover switch, all good, polarity tested fine.

I looked around and I do not see any burnt wires. made sure there not no disconnected/loose wires, all good. I thought on the circuit board and could I pull a code from there. No light to tell me if there was a code. I have 120 V going to the transformer and 28V? coming out. I checked the 3amp fuse on the circuit board, good.

I am to the point of ordering a new circuit board. My fear is if there is something else wrong, I will just blow the new circuit board as well. Am I missing something?
 
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Old 10-30-15, 10:06 PM
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Welcome to the forums.

Measure from R to C at the control board. You should see 24vac.
With the stat in off mode.... measure from R to W..... you should see 24vac.

Don't forget when the blower door is open... the AC power is disconnected.

A model number of the furnace would be helpful too.
 
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Old 10-31-15, 11:45 AM
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I tested on the control board R to C and got 24V, with the button pushed in for AC power. I then tested the R to W with the thermostat in the off position and the button pushed in for A/C power and got .48V.

The model number of the Goodman furnace is GKS9.

Thanks for the help.

Tom
 
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Old 10-31-15, 01:06 PM
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Your manual with diagnostic codes.
Goodman GSK9 manual.pdf

Since you've confirmed 24vac on the C and R terminals that means you have 120vac to the board and 24vac from the transformer. You've also confirmed the plastic fuse is good.

At this point... no LED would indicate defective control board.
 
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Old 10-31-15, 02:54 PM
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>


Yessss.... I would agree. Still, that would be a pretty arare thing to have happen, and I'd want to look for any other possible explanation before replacing the board.


Take the cover off the furnace and find the rating plate in the burner compartment. Post the make and model of the furnace listed on the rating plate.

We may be able to find the circuit diagram and see if any other possible problems suggest themselves.
 
 

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