HVACopediaCarrier · Heat pump
33 Lost inverter communication
What the control is telling you
Amber STATUS light flashes 33. No communication between the AOC board and the inverter (MOC) for 2 minutes. Becomes code 48 after 3 failures within 20 minutes or 20 minutes of continuous loss. Type: Local; reset: Automatic.
Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8 (AOC control + inverter)
Likely causes
- See code 48 for causes
Test and repair steps
- Troubleshoot as code 48.
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Source: Carrier 25VNA8 / 24VNA9 Service Manual, Table 6 Fault Code Actions, p.19. 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.