Aircon shutting off mid-cycle: temperature sensor gone bad
A C4 error and mid-cycle shutdowns usually read as a board or gas problem. On this Daikin in Clementi, the unit cooled fine for ten minutes, then quit. The cause was a small sensor giving a false reading, and the fix took about twenty minutes.
By Team Snowflake | Reviewed 24 Mar 2026
Case summary
Daikin Wall-mounted10 years oldCondoClementi, Singapore
- Concern
- The owner worried the control board had failed, or that the refrigerant system needed a major repair. Both point to a large bill.
- Found
- Liquid pipe temperature sensor was giving false readings
- Key check
- Checked the temperature sensor at room temperature. The reading was clearly wrong.
- Result
- We replaced the temperature sensor, and the unit ran a full cycle without cutting out. It held the room cool with no mid-cycle shutdowns, and the C4 error has not returned since.
What we were told
The aircon starts cooling normally, then shuts off after about ten to fifteen minutes, every time. An error code shows on the display each time it cuts out. The owner said it had been happening more often over the past few weeks. The room never stayed cool because the unit kept stopping before it finished a cycle, then had to be restarted.
What we checked
Cooling that runs well for ten minutes, then stops, told us the main parts were working. A failed board or empty refrigerant would not let the unit cool well at all. The C4 code on a Daikin names the temperature sensor path, so we tested the sensor directly rather than assume a board or refrigerant fault and quote for it.
The C4 code showed on the display after each shutdown.
The unit started and cooled normally for the first ten to fifteen minutes before cutting out.
Wiring between the temperature sensor and the control board was intact, with no corrosion or loose connections.
The temperature sensor reading was clearly wrong at room temperature, which a sound sensor would not give.
The control board responded correctly to all other inputs and commands, so it was not the fault.
What we found
The liquid pipe temperature sensor had drifted out of range after years of heating and cooling. It fed the control board a false reading, so the board thought something was wrong and shut the unit down mid-cycle. The C4 code marks that sensor path. It was not a gas leak and not a board fault.
What fixed it
We explained that the sensor had aged and now read wrong, and that replacing it would clear the C4 code. The board was sound and the refrigerant was fine, so no board swap, gas work, or major repair was needed. The owner agreed to the sensor replacement.
Outcome
We replaced the temperature sensor, and the unit ran a full cycle without cutting out. It held the room cool with no mid-cycle shutdowns, and the C4 error has not returned since.
What this case teaches us
A C4 error points to the sensor, not the whole system
- A unit that cools well for ten minutes, then shuts off, has working parts. That timing argues against a dead board or empty refrigerant.
- On a Daikin, the C4 code names the liquid pipe temperature sensor. The sensor can be tested on its own before anything bigger is touched.
- Before paying for a board swap or gas top-up, ask whether the sensor was checked at room temperature and what reading it gave.
Related reading
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