Lennox HVAC Error Code E36: How to Fix It

Q: What does Lennox error code E36 mean?

Error code E36 means the limit switch has tripped due to overheating or restricted airflow. It's a safety feature that shuts down the furnace to prevent damage.

Q: How do I reset Lennox error code E36?

After fixing the underlying cause (e.g., replacing filter, cleaning vents), turn off power for 5-10 minutes, then restore power. The error should clear. Some units have a manual reset button on the limit switch.

Q: What causes a limit switch to trip on a Lennox furnace?

Common causes include a dirty air filter, blocked vents, a failing blower motor, or a defective limit switch. Less common but serious causes are a cracked heat exchanger or gas valve issues.

Q: Can I replace a Lennox limit switch myself?

Yes, if you are comfortable with electrical work. Turn off power, remove the old switch, and install the correct replacement. However, be sure to diagnose why it tripped first, or the new switch may also trip.

Q: How much does it cost to fix Lennox error code E36?

If DIY, the cost is typically under $50 for a filter and possibly $20-40 for a limit switch. Hiring a professional can range from $150 to $500 depending on the cause.

Abstract

Lennox error code E36 indicates a tripped limit switch, which means your HVAC system is overheating or airflow is restricted. This safety device shuts down the furnace to prevent damage or fire. Follow these steps to safely diagnose and resolve the issue.