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Guyver03 10-22-2006 06:34 PM

Goodman furnace: won't start
Hey all.

It finally got cold enough that we decided to turn on our furnace today, only to find out we're having problems with it. Can't seem to get it to respond at all. I'll try to list all the steps I took to diagnose the problem:

Goodman Furnace
M#: GMPN100-4 Rev B
S#: 0006616767

1) Tried to turn on the furnace. Duh. :laughing:
2) Didn't kick on. Tried to turn on the central air. Didn't start either.
3) Checked breaker for furnace in breaker box. Wasn't tripped.
4) Pulled and checked the plug fuse where the electrical line enters the furnace. Was not blown.
5) Checked switch on incoming power line, was set to on.
6) Status light on PCB will not light up.
7) Pulled fuse on PCB. Was not blown.
8) Checked the door switch, connections seemed solid.
9) Put a meter on the line, and control board gets incoming power.
10) Put meter on the outgoing lines, power does not seem to be exiting the control board.

I'm assuming I have a bad control board, but I'd like to have some more information to go on before I just buy a replacement. Just curious to see if anyone could come up with something to check that I might have missed.

Any info is appreciated and thank in advance. :thumbup1:

#CARRIERMAN 10-23-2006 11:15 AM

Hi Guyver03

Sounds like you could have a limit tripped or a bad transformer, you will need a voltmeter to determin which one. Use a voltmeter on a/c volts, check incoming power to furnace should be 120volts. Then remove blower door, you should see terminals marked sec 1 & 2 on the blower board. Push door switch in on furnace and check for 24 volts. If you have 24 volts at this point, go to your limits. First you will need to turn the thermostat to heat, install blower door, use voltmeter to go from one terminal to the other of your limits. If you read 24 volts across any limits, that limit is open. Some of the limits are resettable, if so look for a button between the two terminals, push hard they are generally hard to reset. If you have no 24 volts after all of this, go to the terminals marked pri 1 & 2, push door switch in and see if you read 120 volts. If you do, you will need to replace transformer. If it is a typical split system it will require a 40va 120 volt transformer. Typical cost for one is around $25.00.

Good luck, let me know if I can help further.

Guyver03 10-23-2006 02:25 PM


Originally Posted by #CARRIERMAN (Post 21601)
Hi Guyver03

Sounds like you could have a limit tripped or a bad transformer, you will need a voltmeter to determin which one.

You're right on! I actually just logged in to tell everyone what I had found in the hopes it would help someone else. It was indeed a bad transformer. Thank goodness too, because I'd rather buy a $22 replacement part over a $200 one any day of the week. :laughing:

Thanks for the help. :thumbup:

I can't for the life of me remember why I didn't check that while I was down there the first time though. Live and learn I guess.

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