Goodman Furnace: Low flame signal, furnace runs normally
Low flame signal, furnace runs normally on a Goodman furnace: The furnace is still lighting and heating, but the flame sense micro amp signal is lower than it should be. A low signal can drop out and cause nuisance lockouts later, so catch it now. Shut the power off and let the burner area cool before reaching in.
Applies to: 34.5 in chassis gas furnaces
Common causes of low flame signal, furnace runs normally
- Flame sensor coated or oxidized
- Flame sensor not positioned correctly in the burner flame
- Lazy burner flame from improper gas pressure or combustion air
How to fix low flame signal, furnace runs normally: step by step
- Turn power off before any repair and let things cool.
- Clean the flame sensor with steel wool if it is coated or oxidized.
- Inspect the sensor for proper alignment in the burner flame.
- Check inlet air piping for blockage, proper length, elbows and termination.
- Compare the current gas pressure to the rating plate and adjust as needed. Gas pressure adjustment is for a licensed gas technician.
- Restore power, run a cycle and recheck the flame signal.
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 Service and Troubleshooting, p. 61. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.