Carrier · Heat pump

31 High pressure switch open

High severity Carrier Infinity 18VS 25VNA8Carrier 2-stage 24ANB/25HNBCarrier single-stage communicating HP

What the control is telling you

Amber STATUS light flashes 31. The high pressure switch opened. The unit waits 6 minutes and restarts one stage lower. If it trips while already on the lowest stage it becomes code 84 (4-hour lockout). Type: Fault; reset: 6 minutes, then runs one stage lower.

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

Likely causes

See code 84 for causes

Test and repair steps

Troubleshoot as code 84 (charge, airflow, closed valve, restriction, HPS wiring).

Models that show this code

15 models in Carrier Infinity 18VS 25VNA8, Carrier 2-stage 24ANB/25HNB, Carrier single-stage communicating HP

25HNB62425HNB63625HNB64825HNB66025HNB92425HNB93625HNB94825HNB96025VNA81325VNA82425VNA82525VNA83625VNA83725VNA84825VNA860

Other codes on the same units

16 Lost communication with user interface
25 Invalid model plug / inverter size
32 Low pressure trip
33 Lost inverter communication
45 Outdoor control board failure
46 Brownout
47 No 230 V at unit
48 Lost inverter communication - lockout

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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.