Goodman GMSS920803BN Error Code 7 Flashes: Low Flame Signal
What Does Code 7 Flashes Mean?
Seven flashes on the Goodman GMSS920803BN diagnostic LED indicate a low flame signal. The furnace is still operating normally for now, but the flame sensor is reading a microamp signal below the expected level. This is a warning that flame detection is degrading.
The flame sensor is a metal rod that sits in the burner flame and generates a tiny electrical current (typically 1-6 microamps) when immersed in flame. The control board monitors this current to confirm the burners are lit. When the current drops below the normal range but is still above the cutoff threshold, this warning code appears.
If left unaddressed, the sensor will continue to degrade until the current drops below the minimum threshold, at which point the furnace will shut down and eventually lock out with a 1-flash code. The most common cause is a buildup of oxidation or combustion residue on the sensor rod. Less commonly, the sensor may be incorrectly positioned in the flame, or low gas pressure may be producing a weak flame.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- The low flame signal code returns after cleaning the sensor
- The flame sensor rod is cracked or visibly damaged
- The flame appears weak, yellow, or uneven across the burners
- The furnace has started locking out with a 1-flash code
- You suspect low gas pressure (other gas appliances also underperform)
✓ Verified against manufacturer service manual — March 2026