Goodman GMVM970803BN Error Code b6: Blower Over/Under Voltage Trip or Over Temperature Trip
What Does Code b6 Mean?
A b6 code on the Goodman GMVM970803BN indicates that the circulator blower motor has shut itself down due to either an abnormal voltage condition or an overheating condition in the motor's power module. The ECM motor has built-in self-protection that monitors incoming line voltage and internal temperatures, shutting down when either parameter exceeds safe limits. The furnace will not operate while this protection is active.
Voltage problems can originate from outside the furnace entirely. Utility power fluctuations, an undersized electrical circuit that sags under load, loose connections in the breaker panel or at the furnace disconnect, or other high-draw appliances on the same circuit can cause line voltage to drop below or spike above the acceptable operating range specified on the furnace rating plate (typically 115 VAC ±10%). Over-temperature conditions in the motor power module can occur if the blower compartment is in an excessively hot utility room, if there is insufficient clearance around the motor for heat dissipation, or if the motor is consistently working at high loads due to restricted airflow from a clogged filter or undersized ductwork.
A qualified HVAC technician or electrician should measure line voltage at the furnace while it is under load and verify it falls within the acceptable range. If voltage is within specification, the over-temperature protection may be triggering — the technician should check for airflow restrictions and ensure the motor has adequate ventilation space.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| High AC line voltage to furnace | Common | ✗ Call a pro → |
| Low AC line voltage to furnace | Common | ✗ Call a pro → |
| High ambient temperatures around blower motor | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Call a technician or electrician to measure line voltage at the furnace disconnect under load — voltage outside the ±10% range requires electrical system repairs before the furnace can operate reliably
- If voltage is correct, the technician should check for airflow restrictions causing the motor to overheat and verify adequate ventilation clearance around the blower compartment
✓ Verified against manufacturer service manual — March 2026