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Error code reference
Lennox Furnace Error Code LED1-FAST_FLASH/LED2-SLOW_FLASH
Main power polarity reversed. Switch line and neutral.
SourceLennox G27M Series Furnace - Service Manualp. 5
Diagnostic procedure
The full LED1-FAST_FLASH/LED2-SLOW_FLASH 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.
MyPros+ · DiagnosticsStep 1 preview
1
First diagnostic step
Check the 120V has line and neutral correctly input into control. Reverse the line and neutral at the 120V field connection.
SourceLennox G27M Series Furnace - Service Manualp. 5
More steps, wiring diagram references, and verified part numbers
Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.
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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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