Weird Issue with Gas Furnace

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Old 02-09-20, 03:08 PM
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Weird Issue with Gas Furnace

Hello and thanks in advance for any help.

I have a Goodman GMP100-3 frunace, manufactured in 1993. I realize that it needs replacing by now, but I need to keep it running until next season.

My issue is this, the furnace will work, but only if I "jump start" it.

To make it work I have to wait until I hear the glow plug click them put a blowtorch flame into the path and it will ignite. HOWEVER it will then work flawlessly for 3 to 5 days without "jumping".

What I have done so far:

Replaced the glow plug
Replaced the flame sensor
Replaced the filter
Removed and wire brushed all the connectors, both to the board and the moving parts, then reconnected them after applying conductive grease to improve connection.

I'm stumped at this point and would appreciate any advice. I'm thinking mainboard but before I go to the expense would like a more professional opinion.

Thanks again,

Paul
 
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Old 02-09-20, 03:28 PM
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Welcome to the forums.

Stop and think about what you are doing. You said the igniter is working but that it won't light the gas. A torch works ok. Then you said you replaced the igniter and still have the same problem. Why ?

It would indicate that the burner is probably rusted and the slots and carryover for the burners are rusted closed. There needs to be gas coming out of the burner where the igniter is.

Have you had this furnace cleaned. Recently ? Ever ?
 
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Old 02-09-20, 05:27 PM
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Pete,

Thanks for the reply.

The furnace was cleaned about 3 years ago and I doubt rust would be the cause (although possible).

I feel I was unclear though. The igniter is NOT working unless I jump start the furnace with a blow torch. After doing that one time the furnace will function perfectly for two to four days, lighting from the igniter which now will magically function.

 
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Old 02-10-20, 09:38 AM
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So the hot surface ignitor isn’t working at all when you have to light the furnace yourself?
 
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Old 02-10-20, 12:46 PM
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Exactly. It is dark and cold when I ignite the flames, but then will work perfectly, turning itself on and glowing and hot for the next few days.

However if I don't ignite the flames then it just stays off. The furnace will cycle but the igniter stays dark.

 
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Old 02-10-20, 03:41 PM
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Ahhh ok. That's different.

You need to monitor the voltage to the igniter. There is usually a plug close to the igniter where you can check for the 120vAC supply. The plug needs to stay plugged in for testing. Your problem sounds like a defective relay on the control board which points towards board replacement.
 
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Old 02-10-20, 03:47 PM
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Test the hot surface ignitor with your meter.
 
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Old 02-10-20, 04:13 PM
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Pete and Roughneck,

Thanks for the replies. I will check the voltage but an intermittently bad relay makes sense. In fact, it would makes more sense if the cold made it worse. That would explain why it works for a few days with the furnace running (warming it up) but when the relay drops below a certain temp it no longer functions.

I will check voltage tonight and thanks again.
 
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Old 02-10-20, 04:42 PM
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I didn't suggest checking the actual igniter since he has already replaced it with no improvement.
The relays found in these control boards leaves a lot to be desired.
 
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Old 02-16-20, 07:35 AM
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One of the things I hate about forums is when someone has a problem, they get several suggestions on how to fix it and then they don't tell you which one worked, so you're just as in the dark as before.

Based on what I'd been told here I got a replacement circuit board (the ICM280, a drop in replacement for the B18099) and installed it in my furnace this morning. So far it's been working perfectly now. Thanks to PJmax and Roughneck77 for the help and tips.
 
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Old 02-16-20, 09:22 AM
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Thanks for letting us know how you made out.
 
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