Fujitsu air conditioner 99 error code: reversing (4-way) valve error

What the 99 code means

Error 99 on a Fujitsu heat pump is a 4-way valve error. The indoor coil temperature does not match the mode: it is too warm in cooling or too cold in heating, compared with the room. The lamps show 9 operation blinks and 9 timer blinks.

A heat pump uses the 4-way valve to swap the direction of refrigerant flow between cooling and heating. Fujitsu's troubleshooting guide says the unit compares the indoor coil temperature with the room temperature. If the coil is more than about 18°F warmer than the room in cooling, or that much colder in heating, two times in a row, the compressor stops.

So 99 can mean the valve did not move, its electrical coil failed, or a sensor is reading wrong.

Common causes

Listed from most to least common.

1. Reversing (4-way) valve stuck or not switching
2. Valve coil or its wiring faulty
3. Indoor coil or room thermistor reading wrong
4. On multi-zone systems, piping and wiring of two rooms crossed

How to fix the 99 code

Unplug the air conditioner or switch it off at the breaker before removing any panel or filter.

1. 1

   Step 1: Reset the power

   Switch off the breaker and disconnect for 5 minutes, then restart in the mode you need.

2. 2

   Step 2: Check the air temperature

   After 10 minutes, feel the air. If the unit blows warm air in Cool or cold air in Heat, the valve is likely not switching. Tell your technician.

3. 3

   Step 3: Think about new installs

   On a new multi-zone system, call the installer. Crossed connections send heating or cooling to the wrong room.

4. 4

   Step 4: Leave it off if it repeats

   If 99 comes back, turn the system off and book service.

How to reset the Fujitsu air conditioner

1. Turn the system off with the remote or wired controller.
2. Switch off the breaker for the system, and the outdoor disconnect switch if there is one. Leave the power off for at least 5 minutes.
3. Restore power and turn the unit back on. The compressor normally waits a few minutes before starting, so give it time before judging.
4. If the same code or blink pattern comes back, the fault is still there. Work through the fix steps above, or call a Fujitsu contractor or other licensed HVAC technician.

When to call a technician

A licensed HVAC technician needs to test the reversing valve coil, its wiring and the sensors. Replacing the valve body means brazing in the refrigerant circuit, which requires EPA certification.

A typical repair for this code costs $250–$1500 in the US, including parts and labor. Prices vary by area and model.

Models this applies to

• Halcyon wall-mounted mini-splits (ASU indoor, AOU outdoor)
• Halcyon floor, ceiling cassette and slim duct units (AGU, AUU, ARU)
• Halcyon multi-zone systems (RLF series)
• Ducted and ceiling-suspended units (RGLX, RULX series)

Codes can differ slightly between models. Your owner's manual is the final word and is available from Fujitsu support.

Frequently asked questions