Lennox HVAC Error Code E35: How to Fix It

Q: What does Lennox error code E35 mean?

Lennox error code E35 indicates that the pressure switch is stuck closed (not opening when it should), usually due to a clogged condensate drain line or a faulty switch.

Q: Can I reset Lennox error code E35?

Yes, you can reset the system by turning the power off at the breaker for 30 seconds and then turning it back on. However, if the underlying issue isn't fixed, the code will return.

Q: How much does it cost to replace a Lennox pressure switch?

A replacement pressure switch typically costs between $20 and $50 for the part. Professional installation can add $100-$200 for service call and labor.

Q: Why does my Lennox HVAC keep showing E35?

Persistent E35 errors often indicate a recurring blockage in the condensate drain or a failing pressure switch. It may also be caused by improper venting or a defective inducer motor.

Q: Can I bypass the pressure switch to fix E35?

No, bypassing the pressure switch is dangerous and can lead to carbon monoxide poisoning or system damage. Always address the root cause.

Abstract

Error code E35 on your Lennox HVAC system indicates the pressure switch is stuck closed or not opening when it should. This typically points to a blockage in the condensate line or a faulty pressure switch. Follow the steps below to diagnose and resolve the issue safely.