What It Means
Inverter DC bus voltage exceeded safe maximum limit.
Bryant Heat Pump
Bryant Heat Pump Error Code 91
Troubleshooting guide for the Bryant Heat Pump system fault 91.
Possible Causes
- Utility line overvoltage condition.
- Open neutral connection in supply wiring.
- Faulty DC bus component on inverter board.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
Inverter VDC-Out Over Voltage Event. Inverter VDC output over-voltage event detected.
All Recorded Causes
Measure supply voltage at outdoor unit for overvoltage. Inspect for utility overvoltage condition. Check inverter board DC bus components. Inspect wiring for open-neutral condition. Board retries after 15 minutes.
Verify Before Replacing Parts
- Confirm the exact Bryant model family and heat pumps context before acting on a generic code description.
- Confirm board LEDs, wiring polarity, and model compatibility before replacing control boards — this Bryant fault points at measure supply voltage at outdoor unit for overvoltage.
- Check for intermittent communication faults caused by connectors, moisture, or damaged harnesses, and rule out inspect for utility overvoltage condition.
- After the correction, run the system long enough to confirm the heat pumps fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Bryant Heat Pump diagnostics step-by-step — so you confirm the cause before swapping parts.
