HVACopediaCarrier · Heat pump troubleshooting
Amber STATUS or green COMM light not on
What is going on
Diagnosing the outdoor AOC board from its two lights.
Likely causes
- AOC board failure
- No communication with the indoor unit / wall control
- Non-communicating thermostat (COMM light is normally off)
Check in this order
- With power to the outdoor unit the amber STATUS light must be on or flashing; if it is completely off, replace the AOC board.
- Communicating systems the green COMM light should be on steady once the indoor unit and Infinity control talk to it; it goes off after 2 minutes without communication.
- If A and B wires are connected and the indoor unit communicates but COMM stays off, replace the AOC board.
- Wall control code 179 = lost communication with the outdoor AOC; the AOC or inverter may need replacing.
Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8
More heat pump guides
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- Outdoor unit unresponsive after several faults
- Outdoor unit will not run - HK32EA defrost board heat pumps
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Source: Carrier 25VNA8 / 24VNA9 Service Manual, Communication and Status Function Lights p.8; LED tables p.27-28. Written in our own words; check the manual for your exact model.
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.