Error code reference

Lennox Furnace Error Code 5+3

No Earth ground; control will restart if error recovers (Board 100869).

SourceLennox G61MP Series - Service Manual: Gas Furnacep. 15

Diagnostic procedure

The full 5+3 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

First diagnostic step

Check that the unit is properly grounded; install a proper main ground.

SourceLennox G61MP Series - Service Manual: Gas Furnacep. 15

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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

7 manuals in the MyPros+ library document this code for Lennox furnace.

Models covered by the manuals that document this code

More models are covered than are listed here.

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The full 5+3 procedure

Where this code is documented

Models covered by the manuals that document this code

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