HeatingCodesFujitsu mini-split blinking lights: how to read the Operation and Timer lamp codes
How the lamp code works
The Fujitsu General America troubleshooting guide (Rev. 5/2019) has a table for wall-mounted units. Each row lists three things for the indoor unit: the Operation lamp blinks, the Timer lamp blinks, and the Economy lamp ("Continuous"). The same row gives the code a wired remote would display. Operation blinks form the first part of the code and Timer blinks the second. 1 and 1 is 11. 3 and 10 is 3A. 10 and 1 is A1.
Common codes
| Code | Lamps (Operation / Timer) | Meaning (per Fujitsu) |
|---|---|---|
| 11 | 1 / 1 | Serial communication error. At startup the indoor and outdoor units are not communicating. The guide says to check wiring from the panel to the condenser and from the condenser to the evaporator and notes that wire nuts and splices are not recommended. |
| 12 | 1 / 2 | Wired remote controller communication error. The indoor unit has not received the wired remote signal for more than 1 minute. |
| 41 / 42 | 4 / 1, 4 / 2 | Indoor room thermistor error (41) or indoor heat exchanger thermistor error (42). |
| 51 | 5 / 1 | Indoor fan motor error. The actual fan frequency is below one third of the target for more than 56 seconds. |
| 74 | 7 / 4 | Outdoor thermistor error. |
| 94 | 9 / 4 | Over current error. Causes listed include a clogged heat exchanger and a defective condenser fan motor. |
| 97 | 9 / 7 | Outdoor fan motor error. Rotation less than 100 RPM within 20 seconds of starting. Causes listed include a locked motor and high temperature around the motor. |
| 99 | 9 / 9 | 4-way valve error. The control compares indoor heat exchanger temperature to room temperature in cooling and heating operation. |
| A1 | 10 / 1 | Discharge temperature error. Protection stop when discharge temperature reaches 230 degrees F (110 C) twice within 24 hours. |
| A5 | 10 / 5 | Low pressure error. Suction pressure stayed very low for 5 minutes, repeated 5 times in 2 hours. |
The full list for these models is in the Fujitsu code table.
Why code 99 matters in heating season
The 4-way (reversing) valve switches the system between cooling and heating. Fujitsu says error 99 is set when the indoor heat exchanger temperature compared with room temperature goes the wrong way two times in a row: in heating the heat exchanger should be warmer than the room, and the guide describes a drop of more than 20 degrees F (10 C) below room temperature as the condition. If a unit runs but blows cold air in heating mode and then shows 99, that points at the valve or related sensors, which need a technician.
What is and is not homeowner work
Fujitsu's guide asks technicians to check connectors, thermistor resistance, voltages and refrigerant. Those steps are not listed here. A homeowner can note the code, check that the outdoor unit is clear of snow and ice, and switch the unit off and on once. The guide's own scope is limited: these are wall-mounted 410A units listed in the guide, not newer R32 models or other Fujitsu families.
Safe homeowner checks for a Fujitsu mini-split error code
- Count both lampsCount the Operation lamp flashes and then the Timer lamp flashes, and write both numbers down.
- Clear the outdoor unitMake sure snow, ice or debris is not blocking the outdoor unit. Clear it gently by hand.
- Restart onceTurn the unit off with the remote, wait a minute, then restart. If the same code returns, stop.
- Call a technicianGive them your model number and the code.
Frequently asked questions
What does the Economy lamp do?
In Fujitsu's wall-mounted table it is listed as "Continuous" for every code, so it does not change the code.
Does this work for every Fujitsu mini-split?
No. The guide has separate tables for other families such as RGLX, multi-zone and cassette units, and newer models differ.
Is Fujitsu 11 the same as Mitsubishi 3 flashes?
They both describe a communication problem between indoor and outdoor units in their own system, but each manufacturer's code is different. Use the table for your brand.
Sources
- 410A Mini-Split Troubleshooting Guide, Part # 6-26-FG2020 (Rev. 5/2019), Wall Mounted table (Fujitsu General America (copy hosted by ilovemyfujitsu.com)) Covers: Fujitsu wall-mounted 410A mini-splits listed in the guide (9RL2, 9RLS3, 9RLS3H, 9RLS3Y, 12RL2, 12RLS3, 12RLS3H, 12RLS3Y, 15RLS3, 15RLS3H, 15RLS3Y, 18RLB, 24RLB, 30RLXB, 30RLXEH, 36RLXB). Other Fujitsu families (floor, cassette, multi-zone, newer R32 units) have different tables.
Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.