HVACopediaCarrier · Heat pump
91 Inverter DC over voltage (event)
What the control is telling you
Amber STATUS light flashes 91. Inverter DC voltage too high, e.g. the compressor suddenly unloaded. After 5 events it becomes code 97. Type: Local; reset: 5 minutes.
Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8 (AOC control + inverter)
Likely causes
- Compressor suddenly unloaded - check service valves are fully open
Test and repair steps
- Check the service valves are fully open.
- If it repeats, troubleshoot as code 97.
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Source: Carrier 25VNA8 / 24VNA9 Service Manual, Table 6 Fault Code Actions, p.25. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.