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Sometimes my goodman gas furnace is opening the main gas…

Sometimes my goodman gas...

Sometimes my goodman gas furnace is opening the main gas valve even tho the pilot is not lighting. This allows gas into the furnace and then the ignitor sparks causing a small explosion in the furnace. If the ignitor does light the pilot the burner comes on immediately with no delay. Seams that the flame sensor is not even in the circuit. If I disconnect the flame sensor after the burner is lit it stays lit even with the sensor disconnected.

Contractor's Assistant: Did you double-check the thermostat? And what about the pilot light?

It has a spark ignitor. Sometimes the pilot lights. Sometimes the ignitor only sparks a couple of seconds and the main valve opens letting gas into the furnace. Then after about a minute the ingitor sparks causing a gas explosion.

Contractor's Assistant: Do you plan on doing the work yourself?

Yes, I am a retired tech. I have been retired long enough that I mostly worked on standing pilot furnaces, not he electronic ones.

Contractor's Assistant: Anything else we should know to help you best?

I'm thinking it is the main board. Probably a relay stuck, causing gas valve to open even tho the pilot isn't lighting?

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Answered in 23 minutes by:
3/7/2018
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,209
Experience: Furnace, A/C and heat pump specialist.
Verified

Sounds like a bad board possibly What is model on furnace?

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Customer reply replied 4 months ago
GDPI100-4

Which ignition module do you have so I can take a look at operation.Some of those old modules sent 24v directly to the valve on call for heat and some made the pilot light first and prove lit before opening main valve.

THere should be either a Honeywell Robertshaw of White Roger number on module

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Customer reply replied 4 months ago
United Technologies
HSC Electronics
B13707-24

Most likely going to be this module bad.

WWe should first get voltage from PV to ignite pilot, but then the sensore should have to verify flame before allowing main valve to get power from MV and open.

https://www.repairclinic.com/PartDetail/Ignition-Module/B1370724/2645929?modelNumber=GDPI100-4

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Customer reply replied 4 months ago
The sensor is not verifying anything. The pilot and burner will ignite without the sensor connected.

Exactly. THat control box SHOULD NOT send 24v to main valve unless the Sensor Proves there is established pilot flame.

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Customer reply replied 4 months ago
I just removed the mv wire from the ingitor control and the pilot lights fine and no gas from main valve, so I guess it is the Ingitor control unit. I will replace it. Thanks, ***** ***** for your help.

Yep.THat should do it.Thanks for letting me work with you.When we are finished if my answer has been polite, professional,and thorough, please click one of the ratings before you go. If you still need help let me know!.Expert is not paid for assisting you until you rate answer.Feel free to follow up for 30 days at no additional cost. Bonus always appreciated if you feel justified.
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Customer reply replied 4 months ago
Will do. Thanks

THank you

airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,209
Experience: Furnace, A/C and heat pump specialist.
Verified
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