Lennox furnace starts and shuts off


Old 01-19-17, 06:36 PM
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Post Lennox furnace starts and shuts off

Furnace was turning on ignitor was glowing , but then the furnace shut off and would re-try. Was told it was a bad ignitor so we replaced it with Lennox ignitor and cleaned the flame sensor. Furnace now turns on, ignitor was glowing but still shuts right off after new install. Now new ignitor isn't even glowing, furnace turns on wheel up top spins turns right off. Its almost like it wasn't getting gas previous but the gas is on and heating the water heater no issues. Any ideas? Its getting cold

Last edited by Ajbrown82; 01-19-17 at 07:03 PM.
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Old 01-19-17, 06:48 PM
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Model: 80UHG3-75A-2 model info
Old 01-19-17, 07:55 PM
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Welcome to the forums.

I'm having a little problem following you and it looks you may some of steps out of order.
Very important... every step must occur at the proper time and last the designated time.

The stat calls for heat.
The draft inducer blower starts up.
The pressure switch closes.
After a prepurge of xx seconds the igniter starts to glow.
After 20-30 seconds the gas valve opens.
The gas valve will only be open for five seconds if the burner doesn't light.
Gas valve closes and igniter shuts off.
The system defaults and tries again.
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