- HVAC
- Air conditioner
11
Fujitsu 11 on an air conditioner: serial communication error
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Fujitsu wall-mounted splits, code 11 (operation 1 blink, timer 1, economy continuous) means the indoor and outdoor units are not receiving the serial signal between them properly. Do one power reset; if it returns, call authorised service.
Safety first
Stop and check this first
- Do not open the outdoor unit or touch the connection terminals: they carry mains voltage and the serial signal is AC too. The user manual says the product contains no user-serviceable parts.
- If you notice a burning smell, Fujitsu says to stop the unit immediately, disconnect all power and consult authorised service.
Safe checks you can perform
- Identify the code from the lamps
- One reset from the breaker
- Note possible interference sources
- Wiring, voltage and serial signal
Leave these tasks to a qualified professional
- Do not attempt this professional task: Terminal voltage measurements
- Do not attempt this professional task: Connection cable inspection
- Do not attempt this professional task: Fan motor test before replacing the board
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Terminal voltage measurements
What they doThe technician measures the supply at L and N and the serial signal at the outdoor unit terminals against the manual's values.
They must show youthe voltages measured at L-N and at the signal terminals compared with Fujitsu's ranges.
In writingcode 11, measured values and diagnosis.
Connection cable inspection
What they doThey check for loose connections, open cables or miswiring between units and correct them per the installation manual.
They must show youthe condition of the terminals and connectors before and after.
In writingwhich connection was corrected and the follow-up operating test.
Fan motor test before replacing the board
What they doIf the signal is abnormal, they test the affected fan motor before replacing the main PCB, as Fujitsu describes.
They must show youthe fan motor test and its result.
In writingpart replaced, reason and date.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Identify the code from the lamps
- Who:
- you, looking at the indoor unit or the wired remote.
- How:
- for 11, Fujitsu describes the operation lamp (green) blinking once, the timer lamp (orange) blinking once and the economy lamp flashing continuously; the wired remote shows 11. The user manual says to consult authorised service when an error code is shown.
- Result that matters:
- confirming it is 11 and not another code with a different blink pattern.
- If the pattern matches:
- continue with the single reset.
- If the pattern differs:
- find its own page; 12, for example, is the wired remote.
- Evidence to keep:
- a short video of the lamps or a photo of the remote showing the code.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG · Fujitsu General operation manual, wall-mounted air conditioner ASYG12KGTF
One reset from the breaker
- Who:
- you, at the consumer unit or the unit's isolator.
- How:
- switch off with the remote, turn off the unit's breaker and turn it back on. The service manual's first step for 11 is to reset the power and operate. Note that, per the user manual, the compressor takes about 3 minutes to start after power returns.
- Result that matters:
- whether the code comes back once the unit is running again.
- If 11 does not return:
- Fujitsu points to an external cause such as electrical noise; note which devices were on nearby.
- If 11 returns:
- do not keep resetting and call authorised service.
- Evidence to keep:
- the date, time, mode in use and whether the code returned and after how long.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG · Fujitsu General operation manual, wall-mounted air conditioner ASYG12KGTF
Note possible interference sources
- Who:
- you, without touching cables or terminals.
- How:
- check whether fluorescent tubes or other electronic equipment sit near the air conditioner's power cable, and whether the fault coincides with switching them on. Fujitsu lists such equipment and poor earthing as external causes.
- Result that matters:
- giving the technician clues on whether the fault is intermittent and external.
- If the fault matches a specific device:
- tell the technician.
- If you see no link:
- the technician will check wiring, voltages and boards.
- Evidence to keep:
- a list of nearby devices and the times the code appeared.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Wiring, voltage and serial signal
- Who:
- a qualified air conditioning technician or authorised service.
- How:
- checks the connection cable and connectors, measures 207 to 253 V AC at the outdoor unit's L and N and checks the signal swings between 90 and 270 V at terminals 1 and 3 (reverse) or between 30 and 130 V at terminals 2 and 3 (forward), as Fujitsu specifies.
- Result that matters:
- whether the fault is in the wiring, the supply, a board or a fan motor.
- If the signal does not swing as it should:
- Fujitsu says to check the fan motor and main PCB.
- If everything measures correctly:
- earthing and external electrical noise are checked.
- Evidence to keep:
- voltages measured at each terminal and wiring condition.
Live measurements at the outdoor unit terminals: risk of electric shock. Qualified technician only.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Fujitsu
- Product type
- Air conditioner
Known code variants
- 11
- Ariston Velis 11
- calentador Rinnai 11
- código 11 Rinnai
- E11
- E:11
- Er 11
- error 11 Rinnai
- Fujitsu 11
- Fujitsu E11
- Rinnai 11
- Rinnai 11 no ignition
- Rinnai code 11
- Rinnai code 11 tankless
- Rinnai error 11
- Toshiba 11
- Toshiba error 11
- Velis error 11
What it means
In the service manual for the ASEH07/09/12/14KMCG series with AOEH outdoor units, Fujitsu General uses E:11 for two cases: the indoor unit receives no signal from the outdoor unit for more than 2 minutes after power on or more than 15 seconds in operation, or the outdoor unit cannot properly receive the indoor signal for 10 seconds or more. Other models may differ. The code alone never proves that a specific part is faulty.
Warnings and stop conditions
- Highsource verified
Do not open the outdoor unit or touch the connection terminals: they carry mains voltage and the serial signal is AC too. The user manual says the product contains no user-serviceable parts.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG · Fujitsu General operation manual, wall-mounted air conditioner ASYG12KGTF
- Mediumsource verified
If you notice a burning smell, Fujitsu says to stop the unit immediately, disconnect all power and consult authorised service.
Evidence: Fujitsu General operation manual, wall-mounted air conditioner ASYG12KGTF
Symptoms and causes
Probable causes · in order
- Connection failure between unitsCommon
A loose or disconnected connection cable, a loose connector, an open cable or miswiring, which Fujitsu says to check after the reset.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
- External cause such as electrical noisePossible
Poor earthing or equipment near the power cable that produces harmonics, such as fluorescent tubes or electronic devices.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
- Supply voltage out of rangePossible
Fujitsu says to check that 207 to 253 V AC is present at the outdoor unit's L and N terminals.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
- Main PCB or fan motorPossible
A main PCB failure, or a fault in the outdoor fan motor (reverse signal) or indoor fan motor (forward signal), depending on which case is detected.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Virtual technician
Does 11 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Fujitsu General · 2024 · manual
- 2
Fujitsu General operation manual, wall-mounted air conditioner ASYG12KGTF
Fujitsu General · manual
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