Gas furnace flame cuts on and off


Old 09-21-19, 12:52 PM
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Gas furnace flame cuts on and off

Hello all. I have a York diamond 80 that wonít stay lit. Replaced flame sensor after low micro amp reading on old one. No change. Found flame will sputter and go out. The itíll reignite. Then sputter and go out. Usually 30 seconds to 2 minutes run time. If I let it try enough it goes into lock out and flashes a code 8. Back probed the gas valve and have 24vac while itís functioning properly, but anywhere from 6vac to 20vac while sputtering. Tested between C and R terminals on controller and voltage goes from 24.7vac with the gas firing up to 25.4vac when the gas sputters off. Seems like the transformer is ok? Am I looking at a circuit board issue? Can any of the switches cause this? Iím not any kind of hvac tech by any means. Iíve also checked the vent and removed the intake filter for testing purposes. Thanks for any ideas!

Last edited by Brett Beckman; 09-21-19 at 02:54 PM.
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Old 09-21-19, 02:29 PM
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Test incoming and manifold gas pressure during the issue. Could be a gas valve or regular issue.
Could also be a heat exchanger problem.
Old 09-21-19, 03:57 PM
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Welcome to the forums.

Back probed the gas valve and have 24vac while it’s functioning properly, but anywhere from 6vac to 20vac while sputtering.
There's your problem. It's either at the plug AT the gas valve or in the 9 or 12 pin connector on the main board. Remove both and reinsert several times and see if it clears up. You can also use a small spray of contact cleaner on the plugs...... not the sockets.

On the back of the blower door should be a wiring diagram. It will show the gas valve connection lines to the large plug. The voltage needs to be checked there too. If not a connector issue..... the relay on the board is most likely bad requiring a board replacement.

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