- HVAC
- Air conditioner
41
Fujitsu 41 on an air conditioner: room temperature sensor open or shorted
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Fujitsu wall-mounted splits, code 41 (operation 4 blinks, timer 1) means the room temperature thermistor is open or short circuited. Turn the power off and on again; if it stays, contact authorized service.
Safety first
Stop and check this first
- Fujitsu warns of electric shock: after switching off, wait 5 minutes before touching electrical components. This unit uses R32 and only staff holding a current certificate may work on the refrigerant circuit.
Safe checks you can perform
- Identify the lamp pattern
- Power reset
- Connector and thermistor measurement
Leave these tasks to a qualified professional
- Do not attempt this professional task: Check connector and sensor before the board
- Do not attempt this professional task: Reset and test
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.
Check connector and sensor before the board
What they doThe technician checks the connector, measures the thermistor and only then considers the main board.
They must show youthe measured thermistor value.
In writingwhat was wrong and what was replaced.
Reset and test
What they doAfter the repair the technician resets the power, as Fujitsu asks, and leaves the unit running.
They must show youthe unit running with no blinking.
In writingdate and result.
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 lamp pattern
- Who:
- you.
- How:
- count the blinks of the operation lamp (green) and the timer lamp (orange), or read the wired remote.
- Result that matters:
- 4 operation blinks and 1 timer blink, or 41.
- If it matches:
- it is the room sensor; the owner manual says to consult authorized service.
- If it is 4 and 2:
- it is code 42, the heat exchanger sensor; do not mix up pages.
- Evidence to keep:
- a video of the lamps and the date.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Power reset
- Who:
- you.
- How:
- turn off the unit's circuit at the consumer unit, wait a few minutes and restore power.
- Result that matters:
- whether the code returns once it runs.
- If it does not return:
- note the date; Fujitsu clears the stored error after 2 hours without faults.
- If it returns:
- the fault is still present; call a technician.
- Evidence to keep:
- a note of each occurrence.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Connector and thermistor measurement
- Who:
- an air conditioning technician.
- How:
- checks the thermistor connector on the board and measures the thermistor with a multimeter.
- Result that matters:
- whether the connector was loose or the sensor measures out of value.
- If the connector was loose:
- it is reseated, power is reset and the cause is confirmed.
- If connector and sensor are fine:
- it points to the main board.
- Evidence to keep:
- a job sheet with the measured value and photos of the connector.
Requires isolating power, waiting 5 minutes and opening the unit: 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
- E41
- E:41
- Fujitsu 41
- Fujitsu E41
What it means
In Fujitsu's ASEH KMCG service manual, code 41 is set when the control continuously detects the room temperature thermistor as open or short circuited. Fujitsu cites the connector, the thermistor itself or the main board, and asks for a power reset after a removed connector or wrong wiring has been put right. The code does not say which of the three has failed: a technician's measurement separates them.
Warnings and stop conditions
- Highsource verified
Fujitsu warns of electric shock: after switching off, wait 5 minutes before touching electrical components. This unit uses R32 and only staff holding a current certificate may work on the refrigerant circuit.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Symptoms and causes
Probable causes · in order
- Thermistor connectorPossible
A loose or misplaced connector gives an open reading even with a good sensor. It is fixed by reseating it and resetting power.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
- Faulty thermistorPossible
If the connector is fine, a sensor resistance out of value confirms the sensor as the cause.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
- Main boardPossible
If connector and thermistor are fine and the code persists, Fujitsu points to the main board.
Evidence: Fujitsu General air conditioner wall mounted type service manual, ASEH07/09/12/14KMCG and AOEH07/09/12/14KMCG
Virtual technician
Does 41 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
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