Fujitsu Error Code 31: Power supply interruption error (Heat Pump)

Updated October 13, 2026 · by Aurora Star Tech Inc.

Fujitsu error code 31 on a heat pump means: Power supply interruption error. It is also called Fujitsu diagnostic code 31.

Low severityHeat PumpFujitsu ductless split/multi/VRF (general code list) · Fujitsu slim duct ARU 7-18 (LL type)

Homeowner? What Fujitsu code 31 means for you

Usually minor Your heat pump is reporting: Power supply interruption error. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
In winter, keep snow and ice off and away from the outdoor unit. A short defrost cycle with steam is normal.
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Fujitsu error code 31 mean?

A power interruption was detected. Indoor lamps: OPERATION (green) flashes 3x, TIMER (orange) flashes 1x, ECONOMY (green) flashes fast nonstop; wired remote shows 31.

Applies to: Fujitsu ductless heat pumps: Fujitsu ductless split/multi/VRF (general code list), Fujitsu slim duct ARU 7-18 (LL type)

Common causes of Fujitsu code 31

Momentary power loss
Loose supply connection

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Other Fujitsu Heat Pump codes

Code	Meaning
22	Indoor unit capacity error
23	Combination error
24	Connection unit number error
26	Indoor unit address setting error
27	Primary / secondary unit setup error
29	Connection unit number error (wired remote system)
32	Indoor main PCB error (EEPROM / model info)
33	Indoor fan motor power consumption error
35	MANUAL AUTO button error
39	Indoor fan motor power supply error
41	Room (intake air) temperature sensor error
42	Indoor coil (heat exchanger middle) sensor error

All Fujitsu Heat Pump error codes →

Fujitsu code 31: homeowner questions

What does Fujitsu code 31 mean?

Power supply interruption error. A power interruption was detected. Indoor lamps: OPERATION (green) flashes 3x, TIMER (orange) flashes 1x, ECONOMY (green) flashes fast nonstop; wired remote shows 31.

Is it safe to keep using my heat pump with code 31?

Usually yes. Code 31 is normally minor, but if it keeps coming back have it checked.

Can I reset Fujitsu code 31 myself?

You can try one reset (power off for 30 seconds, then on). If Fujitsu code 31 comes back, the cause is still there and a licensed technician should check it.

Who can fix Fujitsu code 31 near me?

Aurora Star Tech Inc. repairs Fujitsu heat pumps in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: AC Running But Not Cooling: What to Check · Heat Pump Not Heating or Blowing Cold Air

Source: Fujitsu All Fujitsu split - multi - VRF (generic code list) codes.pdf - section error code table (indoor LED flashes); Fujitsu Slim duct AR07-09-12-14-18 (ARU-ARYG LL-type equivalent) installation P-N 9381858064.pdf - section 14 Error codes. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.