Lennox Furnace Error Code LED1-SLOW_FLASH/LED2-ON
Primary or secondary limit open. Units with board 63K8901 or 24L85: Limit must close within 5 trials for ignition or board goes into one hour limit Watchguard. Units with board 56L83 or 97L48: Limit must close within 3 minutes or board goes into one hour limit Watchguard.
SourceLennox G27M Series Furnace - Service Manualp. 5
The full LED1-SLOW_FLASH/LED2-ON procedure
Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.
SourceLennox G27M Series Furnace - Service Manualp. 5
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Where this code is documented
2 manuals in the MyPros+ library document this code for Lennox furnace.
Models covered by the manuals that document this code
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