Lennox HVAC Error Code E9: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
Summarize with ChatGPTSummarize with ClaudeSummarize with Perplexity Add as Preferred Source on Google
Error Code
E9
Brand
Lennox
Product Type
hvac
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code E9 on your Lennox HVAC system indicates a fault with the outdoor coil temperature sensor. This sensor monitors the temperature of the outdoor coil to ensure efficient operation. When it fails, the system may not run correctly or may shut down to prevent damage.
Ad

Tools You'll Need

How to Fix Error Code E9

  1. Turn Off Power

    Always disconnect power before servicing. High voltage components can cause serious injury or death.

  2. Locate the Outdoor Coil Sensor

  3. Inspect the Sensor Wiring

  4. Clean the Sensor

  5. Test the Sensor Resistance

    Handle the multimeter probes carefully to avoid shorting.

  6. Replace the Sensor if Faulty

  7. Restore Power and Test

Parts You May Need

Outdoor coil temperature sensor
Check Price on Amazon
Outdoor coil temperature sensor
Check Price on Amazon
Outdoor coil temperature sensor
Check Price on Amazon
Outdoor coil temperature sensor
Check Price on Amazon
Ad

When to Call a Professional

If the error code remains after replacing the sensor, or if you are uncomfortable working with electrical components, call a licensed HVAC technician. The issue could be with the control board or wiring harness.

Frequently Asked Questions

What does Lennox error code E9 mean?
Error code E9 indicates a fault with the outdoor coil temperature sensor. This sensor monitors the temperature of the outdoor coil, and a failure can cause the system to shut down or operate inefficiently.
Can I drive my car with error code E9?
No. Error code E9 is for HVAC systems, not vehicles. If you see this code on your car, refer to your vehicle's manual.
How do I reset Lennox error code E9?
Simply turning the system off and on may clear the code temporarily. However, if the sensor is faulty, the code will return. The proper fix is to test and replace the sensor if needed.
Where is the outdoor coil sensor located on Lennox HVAC?
It is typically attached to the copper tubing of the outdoor coil, near the service valves. Open the access panel to locate it.
How much does it cost to replace a Lennox outdoor coil sensor?
The sensor itself can cost $20 to $50. If you hire a technician, labor charges may add $100 to $200.

Related Error Codes