Goodman GMSS960803BN Error Code Continuous/Rapid Flash: Reversed Polarity
What Does Code Continuous/Rapid Flash Mean?
A continuous rapid flash on the Goodman GMSS960803BN diagnostic LED indicates that the 115-volt or 24-volt power supply has reversed polarity. The control module checks that the hot wire reads approximately 115 volts to ground and the neutral reads 0 volts. If these are reversed, the furnace shuts down for safety.
The most common cause is the 115-volt AC hot and neutral wires being swapped at the furnace disconnect, the electrical panel, or at the receptacle if the furnace uses a plug connection. This can happen after electrical work, a panel upgrade, or if the furnace was recently installed.
Reversed transformer wires (the orange and gray wires on this model) can also trigger the code at the 24-volt level. Additionally, a poor or missing earth ground can cause the control module to misread polarity even when the wires are connected correctly. An electrician or HVAC technician should verify the wiring and ground connection.
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 LED flashes continuously and the furnace will not operate
- The furnace was recently installed or had electrical service work
- Other equipment in the home shows signs of electrical wiring issues
✓ Verified against manufacturer service manual — March 2026