Lennox HVAC Error Code E34: How to Fix It

Q: What does Lennox error code E34 mean?

Error code E34 means the pressure switch in your Lennox HVAC system is not closing. This indicates a problem with airflow, blocked venting, or a faulty switch.

Q: Can a dirty air filter cause E34?

Yes. A dirty air filter restricts airflow and can cause the pressure switch to fail to close. Always check and replace the filter first.

Q: How do I reset my Lennox system after fixing E34?

Turn off the power at the breaker for 30 seconds, then turn it back on. The system should attempt a normal startup. If the error returns, further troubleshooting is needed.

Q: Is it safe to bypass the pressure switch?

Never bypass the pressure switch. It is a safety device that prevents operation if flue gases are not properly vented. Bypassing can lead to carbon monoxide poisoning.

Abstract

Lennox error code E34 means the pressure switch in your HVAC system is not closing. This typically indicates a problem with airflow, a blocked vent, or a faulty pressure switch. Follow these steps to diagnose and fix the issue safely.