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Error code reference
Lennox HVAC Error Code 103
The 24VAC to the air-handler control is lower than the required range of 18 to 30VAC.
SourceLennox CBX40UHV - Service Manual: Installation & Service (HFC-410A)p. 35
Diagnostic procedure
The full 103 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 and correct voltage. Check for additional power-robbing equipment connected to system. May require installation of an additional or larger VA transformer.
SourceLennox CBX40UHV - Service Manual: Installation & Service (HFC-410A)p. 35
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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