Goodman GMSS960803BN Error Code 5 Flashes: Flame Sensed With No Call for Heat
What Does Code 5 Flashes Mean?
Five flashes on the GMSS960803BN's Integrated Control Module indicate flame is being sensed when the thermostat is not calling for heat. Because the board is reading a flame signal it should not see, it locks out heating and runs both the inducer and the circulator blower continuously — a safety response meant to clear the cabinet in case any combustion is genuinely occurring.
The flame sensor confirms a real flame by passing a tiny microamp current through the flame to ground. This code is essentially that circuit lying to the board: it reports current when the gas valve should be closed and no flame should exist. Goodman attributes it to a short to ground in the flame-sense circuit — for example a chafed or pinched sensor wire touching the metal chassis, which completes the same electrical path a real flame would.
A flame sensor rod that is physically contacting grounded metal produces the identical symptom. The rod is supposed to be isolated by its white ceramic insulator; if that insulator cracks or the rod shifts, the rod-to-ground contact fakes a flame signal. It is worth distinguishing this from the 7-flash low-flame-signal code: seven flashes is too little flame current during normal firing, while five flashes is flame current present when there should be none. Both live in the flame-sense circuit but describe opposite faults.
What You'll Notice
- Both the inducer and the circulator blower run non-stop, even with no call for heat
- The furnace will not perform a normal heating cycle
- The diagnostic LED blinks five times, pauses, and repeats
- No visible flame at the burners despite the continuous blower operation
- Blowers may keep running after the thermostat is satisfied or turned down
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Short to ground in flame sensor wiring | Most common | ✗ Call a pro → |
| Faulty flame sensor rod touching ground | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician confirms there is genuinely no flame present, then treats the fault as an electrical short in the flame-sense circuit. With power off, they inspect the flame-sensor wire for chafing, pinch points, or spots where it contacts the chassis, and check the sensor rod and its ceramic insulator for cracks or contact with grounded metal. The short is repaired or the sensor replaced as needed. Because this is electrical fault-finding in a safety circuit, it is professional work rather than a homeowner task.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- Both blowers run continuously and the furnace will not cycle normally
- The LED shows five flashes with no flame visible at the burners
- The flame-sensor wire looks chafed, pinched, or is touching metal
- The sensor's white ceramic insulator is cracked or the rod has shifted
Frequently Asked Questions
Why do both blowers on my Goodman GMSS960803BN run non-stop?
With a 5-flash code the board thinks it senses flame when none was called for, so it runs the inducer and circulator continuously as a safety measure to clear the cabinet. The blowers keep running until the false flame signal is corrected.
Is a 5-flash code dangerous?
The furnace is deliberately protecting you by purging with both blowers, but the underlying short in the flame-sense circuit needs repair so the safety system reads correctly. Have a technician find and fix the short rather than ignoring it.
Can I just clean the flame sensor to fix 5 flashes?
No. Cleaning addresses a weak signal (the 7-flash code), whereas 5 flashes is a short to ground creating a false flame signal. It requires finding a chafed wire or a grounded rod, which is a professional electrical repair on this furnace.
✓ Verified against manufacturer service manual — March 2026