Lennox iComfort thermostat shows E312 indoor blower fault when cooling is requested; outdoor unit may run but little or no air comes from vents.

Safety: Turn off power to the furnace/air handler at the breaker. Blower compartments contain moving parts and live electrical connections.

• 1. Check blower operation: Set thermostat fan to ON. If the blower does not run, the issue is likely with the motor, control module, or power supply.
• 2. Inspect wiring harness: Remove the blower access panel. Verify the multi-pin harness to the Lennox ECM motor is fully seated and not damaged. Reseat connectors.
• 3. Spin blower wheel by hand: With power off, try to rotate the blower wheel. It should spin freely. If it is stiff or scraping, debris or a failed bearing may be present. Clean and re-center the wheel or replace the assembly.
• 4. Check for error LEDs on control board: Many Lennox boards flash codes indicating motor faults. Note the pattern and consult the unit's service label for interpretation.

Note: ECM motors and modules are expensive and require correct Lennox replacement parts. Have a technician test motor windings and module before replacement.