Rheem HVAC Error Code 5: How to Fix a Weak Flame Sensor

Q: What does error code 5 on Rheem HVAC mean?

Error code 5 indicates a weak flame sensor. The sensor is not detecting the burner flame properly, causing the system to shut down as a safety precaution.

Q: Can I clean the flame sensor myself?

Yes, cleaning the flame sensor is a straightforward DIY task. Power down the unit, remove the sensor, gently sand the rod, and reinstall. Always follow safety precautions.

Q: How often should I clean the flame sensor?

For most systems, cleaning the flame sensor every 1-2 years as part of routine maintenance can prevent error codes and ensure reliable operation.

Q: What happens if I ignore error code 5?

Ignoring this error may lead to intermittent heating, frequent cycling, and eventually a complete lockout of the furnace. Continued operation with a weak sensor can also cause increased wear on other components.

Q: How do I know if the flame sensor needs replacement?

If cleaning does not resolve the error, the sensor may be faulty. Use a multimeter to test resistance; a good sensor typically shows low resistance (around 0-100 ohms). Replace if open or high resistance.

Abstract

Error code 5 on a Rheem HVAC system means the flame sensor is weak or failing. This sensor detects the burner flame and signals the control board. When it weakens, the furnace may ignite briefly then shut off. Cleaning or replacing the flame sensor usually resolves the issue.