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Error code reference
Lennox Heat Pump Error Code 12
Problem with the operation of the outdoor temperature sensor.
SourceLennox HP21 Series - Full Service Manual (Heat Pump)p. 15
Diagnostic procedure
The full 12 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 outdoor temperature sensor and wiring.
SourceLennox HP21 Series - Full Service Manual (Heat Pump)p. 15
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 heat pump.
Models covered by the manuals that document this code
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