Lennox Furnace Error Code E300: How to Fix It

Q: What causes Lennox E300 error code?

E300 error occurs when the limit switch stays open for over 3 minutes, typically due to overheating from dirty air filters, blocked vents, dirty blower components, or a faulty limit switch.

Q: Can I reset Lennox E300 error myself?

You can reset the error by turning the furnace off for 30 seconds then back on, but the underlying cause must be fixed or the error will return. Always address the root cause before resetting.

Q: Is Lennox E300 error dangerous?

Yes, E300 is a critical safety error indicating overheating. The furnace shuts down to prevent damage or safety hazards. Never ignore this error or bypass safety switches.

Q: How often should I change my furnace filter to prevent E300?

Change standard filters every 1-3 months depending on usage and home conditions. High-efficiency filters may last 6-12 months. Regular filter changes prevent most E300 errors.

Abstract

Lennox furnace error code E300 indicates the limit switch has been open for longer than 3 minutes, which is a critical safety issue. This error typically occurs when your furnace is overheating due to restricted airflow, a dirty filter, or a faulty limit switch component.