Error code reference

Lennox HVAC Error Code 353

There is a problem with the air-handler's third stage electric heat (pilot relay contacts did not close or relay coil did not energize); air-handler will operate on first stage only.

SourceLennox CBX40UHV - Service Manual: Installation & Service (HFC-410A)p. 36

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Diagnostic procedure

The full 353 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 relay coil and contacts. The alarm clears after stage 3 relay is detected.

SourceLennox CBX40UHV - Service Manual: Installation & Service (HFC-410A)p. 36

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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 hvac.

Models covered by the manuals that document this code

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The full 353 procedure

Where this code is documented

Models covered by the manuals that document this code

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