Lennox Error Code F1
Return air temperature sensor fault
Error Code Summary
| Brand | Lennox |
| Error Code | F1 |
| Meaning | Return air temperature sensor fault |
| Cause | Room temperature thermistor open or short circuit |
| Recommended Action | Check sensor wiring, measure resistance, replace thermistor if out of spec |
How to Fix Lennox Error F1
- 1
Power Cycle the Unit
Turn off the unit at the breaker, wait 5 minutes, then restore power. Some errors auto-clear after a restart.
- 2
Identify the Issue
Error F1 means: Return air temperature sensor fault. The most common cause is: Room temperature thermistor open or short circuit.
- 3
Take Corrective Action
Check sensor wiring, measure resistance, replace thermistor if out of spec
- 4
Test the System
After completing repairs, run the system and monitor for the error code. If it recurs, the issue may require professional diagnosis.
Safety Notice
Always disconnect power before performing any electrical work. If you're not a certified HVAC technician, contact a qualified professional for repairs involving refrigerant, electrical components, or compressor work.
Frequently Asked Questions
What does Lennox error code F1 mean?
Lennox error code F1 indicates: Return air temperature sensor fault. This is typically caused by: Room temperature thermistor open or short circuit.
How do I fix Lennox error code F1?
To fix Lennox error code F1: Check sensor wiring, measure resistance, replace thermistor if out of spec. If the error persists after these steps, contact a qualified HVAC technician.
Is Lennox error code F1 serious?
Error code F1 (Return air temperature sensor fault) should be addressed promptly to prevent further damage to your Lennox system. Always turn off the unit if you notice unusual sounds, smells, or continued malfunction.