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Carrier · Heat pump

25 Invalid model plug / inverter size

High severity Carrier Infinity 18VS 25VNA8Carrier 2-stage 24ANB/25HNB

What the control is telling you

Amber STATUS light flashes 25. The AOC board cannot read a valid model plug, or the plug does not match the inverter size, so the unit will not run. Type: System malfunction; reset: None (fix and power cycle).

Applies to: Carrier Infinity 18VS variable speed heat pump 25VNA8 (AOC control + inverter)

Likely causes

  • Model plug missing, damaged, corroded or not fully seated
  • Wrong model plug for this unit
  • Plug size does not match the inverter size (e.g. 2-ton plug with 3-ton inverter)
  • Failed AOC board

Test and repair steps

  1. Check the plug is present and seated per the silkscreen on the AOC board.
  2. Confirm the plug part number for the unit size (model plug table in the manual) and measure its resistance (pins 1-4 and 2-3) against the wiring diagram.
  3. Replace a wrong or damaged plug; if plug and inverter match and are good, replace the AOC board.

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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.