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.
The 24VAC to the air-handler control is lower than the required range of 18 to 30VAC.
First step from the service manual
Check and correct voltage. Check for additional power-robbing equipment connected to system. May require installation of an additional or larger VA transformer.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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Get the full diagnostic procedure for 103.
- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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