E439
Lennox
Blower Motor Communication / ECM Fault (Communicating System)
Thermostat shows E439; furnace may not start or may shut down mid-cycle.
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Failed Lennox variable-speed ECM blower motor, Loose ECM harness connector, Faulty blower motor control module, Overheated blower due to restricted airflow
How to Fix / Troubleshooting
Safety: Turn off power before accessing the blower compartment.
- 1. Inspect blower wheel and filter: Ensure the filter is clean and the blower wheel is not packed with dust, which can overload the motor.
- 2. Check ECM harness: Locate the ECM motor on the blower housing. Verify that the multi-pin control connector and power connector are fully seated and undamaged.
- 3. Allow cooling: If the blower is very hot to the touch, allow it to cool for 30–60 minutes, then restore power and test.
If E439 returns, the ECM motor or its control module likely requires professional testing and replacement.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Lennox ECM Blower Motor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements