Lennox gas furnace issue

Old 01-05-17, 06:11 AM
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Lennox gas furnace issue

I got a Lennox 80MGF furnace. Starting from yesterday I got rollout issue. When there is a call for heating, the furnace would start properly. However after about 1 mininute running, the gas valve would close to shut down combustion and 2 LED on the board indicate rollout switch is open. I disconnected wiring to those 2 rollout switches and my multimeter shows none of them is open. Reconnected the wiring and then checked voltage on each side of 2 rollout switches. All the readings are around 27V AC, which matches the continuity check on the rollout switches previously. Has anyone experienced similar issues in the past?

House temperature is dropping. Any help is greatly appreciated.
Old 01-05-17, 07:12 AM
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Be sure and check the Hi limit switch. It's is in the same circuit as the roll out's. According to the manual 2 flashes indicate flame failure. Clean the flame sensor and see if that corrects the problem.

Last edited by skaggsje; 01-05-17 at 07:19 AM. Reason: added
Old 01-05-17, 11:10 AM
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The manual I'm looking at uses two LED's for diagnostics.


If you were having a flame rollout problem the button should pop out on the back of the switch. I would expect to see flames coming out of the burning chamber too.

What was the exact code you saw ?

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