Goodman GMSS920803BN Error Code Continuous/Rapid Flash: Reversed Polarity
What Does Code Continuous/Rapid Flash Mean?
A continuous rapid flash on the Goodman GMSS920803BN diagnostic LED indicates reversed electrical polarity. The control module has detected that the 115-volt or 24-volt power supply wires are reversed, and it will not allow the furnace to operate until the wiring is corrected.
The most common cause is the 115-volt AC hot and neutral wires being swapped at the furnace connection point. This can happen during installation, after electrical work on the home's panel, or if the furnace is plugged into a receptacle with reversed wiring. On this model, the transformer's orange and gray wires being reversed can also produce this code.
A poor or missing unit ground can interfere with the control module's ability to detect polarity correctly, sometimes triggering this code even when the hot and neutral are wired correctly. An electrician or HVAC technician needs to verify the polarity at the furnace and correct any wiring issues.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| 115V AC power wires reversed | Most common | ✗ Call a pro → |
| Transformer wires (orange and gray) reversed | Common | ✗ Call a pro → |
| Poor or missing unit ground | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace LED flashes continuously and the unit will not operate
- The furnace was recently installed or had electrical work performed
- You suspect the home's electrical outlets may have reversed polarity
✓ Verified against manufacturer service manual — March 2026