HVACopediaCarrier · Heat pump
48 Lost inverter communication - lockout
What the control is telling you
Amber STATUS light flashes 48. Communication between AOC and inverter (MOC) keeps failing (elevated from code 33). The system retries starting on its own. Type: System malfunction; reset: Automatic retries.
Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8 (AOC control + inverter)
Likely causes
- Loose or disconnected harness between AOC (PL20) and inverter
- Electrical noise / radio interference
- Damaged inverter
Test and repair steps
- Check and reseat the harness between the AOC board and the inverter.
- Look for sources of electrical noise near the wiring.
- If the harness is good and the fault returns, replace the inverter drive.
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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.
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