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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8253
Experience:  Furnace, A/C and heat pump specialist.
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GMS81155CNBD... will flame up on a heat request but doesnt

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GMS81155CNBD... will flame up on a heat request but doesn't stay lit, maybe 3-5 seconds... process repeats approx every 20 sec... no LED indicator on the control panel... any ideas?
Hello. My name is XXXXX XXXXX I'll do my best to help. Troubleshooting often requires meters and test equipment. Let's get started and see what we can do.
Did you try cleaning the flame sensor? It is a small steel rod sticks in flame in front of last burner. Often will build up with carbon and doesnt since flame.
Customer: replied 3 years ago.

the only rod i see is the glow rods to ignite the gas on the far right

On one end of the burners should be the glow bar that lights the burners. Then on the farthest burner away should be the flame sensor. It will have one wire attached ,usually red or orange wire.
You can see what it looks like here:
Customer: replied 3 years ago.

oh i see it now, big as day... it looks pretty clean but i will give it a good scrub and try again-


"what if" that is not the issue? what would my next step be?

We really should be getting an error code at this point if it does not stay lit.That would tell us what failed. We may have an issue with the board if it does not light and does not give an error code.
Customer: replied 3 years ago.

no need to check further, it was the flame sensor... once i pulled it out it clearly had buildup on it-



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