Error code reference
Lennox Hvac Error Code 105
The iComfort thermostat has lost communication with the air-handler for more than 3 minutes.
The iComfort thermostat has lost communication with the air-handler for more than 3 minutes.
First step from the service manual
Check the wiring connections, ohm wires and cycle power. The alarm stops all associated HVAC operations and waits for a heartbeat message from the unit that's not communicating.
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 105.
- 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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