Goodman GDS80904BX New Install - Won't Light


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Old 10-30-14, 01:23 AM
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Goodman GDS80904BX New Install - Won't Light

Hello all!

I have researched a good deal of threads on this subject here and elsewhere, and the problem seems to be a common one:

1) On call for heat, the inducer starts - runs for 15 seconds
2) I hear a click on the control board, the ignitor lights and glows bright orange
3) I never hear any click in the gas valve, don't hear any gas flowing, and no flame ever appears
4) After about 5 seconds there is another click, the ignitor goes out, and the inducer stops
5) Process repeats 3 times until lockout

I have checked many of the things that have been referenced in other similar threads - checked connections to all switches/sensors; checked tube to pressure switch for clogs, etc. The difference in my situation is this is a new install - the unit has never been in service; although it has been in storage in my garage for a couple of years. There is no indication of any kind of damage; all wiring seems to be there with no broken wires or obvious problems. Unit is completely clean - no dust or cobwebs in any of the openings. I did a careful install of the electrical, with a good ground to the same screw as the green ground wire from the control panel. Venting is installed temporarily - all connections are slip fit but no screws installed yet. The return ducting is loosely in place, but I haven't taped or sealed any of the joints yet as I wanted to make sure it would fire before I locked everything down.

Gas supply is fine - unit is sitting right next to (and shares a gas line with) my hot water heater which runs as needed. I quickly cracked the shutoff valve for the furnace with the flexible supply line disconnected, and heard and smelled gas so I know it is flowing to the gas valve. Thermostat and wiring seems fine.

The one thing I haven't checked is voltage at the gas valve - my multimeter is at my other house and I have to make a trip over to pick it up. I'll do that as soon as possible, but I thought I would post here to see if anyone has any other specific advice for a new install. There shouldn't be any issues with the flame sensor, heat exchanger, control board since the unit has never seen any use.

Anyway, hope to hear from you guys with some things to check I haven't thought of yet.

Thanks

Dave
 
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Old 10-30-14, 07:23 AM
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Welcome to the forums.

Since it's a brand new furnace it could be anything. You are going to need that voltmeter otherwise you're just guessing. Have you checked the obvious.... loose wire or brokenwire at the control board and at the gas valve ?

It's not a flame sensor "problem". The flame sensor is not detecting a flame and stopping the heating process but it's not the problem..... it's working correctly.
 
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Old 10-30-14, 08:55 PM
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Update:

Voltmeter shows no 24VAC going to gas valve during startup sequence. I checked the transformer and it has 40VAC unloaded, so I believe 24VAC is present. I traced continuity through the Aux Limit switch (I believe that is what it is called - it is inside the blower cabinet - brown wires). The other wire goes directly to the control board - blue wire. Both show full continuity, so no broken wires or defective connections.

So it would appear most likely in the control board. I can get a direct replacement for about $50. It seems strange that a never-used unit might have a defective board, but I'm an electronics guy and I've seen it happen.

Anybody have any other advice before I place the order?

Dave
 
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Old 10-30-14, 09:15 PM
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A 24vac transformer should not measure 40vac unloaded. It should never be even over 30vac.
Are you sure you measured it correctly ?

Why are you buying a board for a new install ??
Is this a used furnace ?

If you had 24vac on the gas valve it should have opened.
 
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Old 10-31-14, 05:43 PM
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Thanks for the reply.

I guess I didn't think much of the overvoltage at the transformer. I typically work with DC supplies that are higher than needed and regulated downstream; so it didn't jump out at me. That made me suspect my meter - I measured again and got 39VAC on the secondary of the transformer. I also measured the primary, which showed 148VAC; which would be of concern to me if I really believed it. I think my meter is wonky - maybe the battery is dying.

Anyway, all that is history because the unit is now working. I suspect all the probing might have resulted in me inadvertently fixing a poor connection. I also redid the supply wiring with particular attention to grounding. Whatever it was, the furnace now lights and I am spending my time buttoning up the venting and return air ducting.

Thanks for the assistance,

Dave
 
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Old 10-31-14, 07:31 PM
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You are very welcome. If you're using a digital meter... it may need a battery change.
 
 

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