Error code reference

Lennox Air Conditioner Error Code 1

Power loss for two electrical cycles (33-40 milliseconds), suggesting dirty or low quality power to the unit.

SourceLennox HS21 Series - Service Manual: Air Conditioner Unitsp. 10

Lennox codes Lennox air conditioner codes

Diagnostic procedure

The full 1 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 power quality to the unit.

SourceLennox HS21 Series - Service Manual: Air Conditioner Unitsp. 10

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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

1 manual in the MyPros+ library documents this code for Lennox air conditioner.

Models covered by the manuals that document this code

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The full 1 procedure

Where this code is documented

Models covered by the manuals that document this code

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