Started short cycling after service: sensor knocked out of clip
The unit cooled fine before the service visit. Right after, it began cutting off every few minutes, then restarting on its own. The servicing company returned and said the temperature sensor had failed and needed replacing. The timing pointed somewhere else.
By Team Snowflake | Reviewed 10 Mar 2026
Case summary
Midea Wall-mounted4 years oldHDBPaya Lebar, Singapore
- Concern
- The client feared the service work had damaged the control board, meaning a costly electronic repair.
- Found
- temperature sensor was displaced from its clip during servicing, reading room air instead of coil temperature
- Key check
- Checked sensor position and reading against coil surface temperature to confirm displacement
- Result
- The short cycling stopped at once. The unit ran a full cooling cycle and held its set temperature without cutting off early.
What we were told
The aircon was working fine until another company came to do a general service. After they left, it started turning off after a few minutes, then restarting. It keeps cycling on and off. They came back and said the temperature sensor had failed and needed replacing.
What we checked
Because the fault started right after the service, we checked the sensor position before testing any electronics. We removed the front cover and filter panel to reach the coil. Then we looked at whether the temperature sensor still sat in its clip on the coil surface. We also compared its reading against a contact thermometer on the coil, to see what the board was being told versus the real coil temperature.
The temperature sensor hung loose inside the unit, no longer clipped to the coil.
Its reading matched room temperature, not the cooler coil surface it should track.
The control board responded correctly to that reading. It worked as designed, but on wrong data.
What we found
During the earlier service, the temperature sensor was knocked out of its clip on the coil. The clip is small and the probe sits in a narrow channel along the coil surface, so a cleaning brush or a refitted filter panel can dislodge it. Once loose, the probe hung in the airstream and read room air instead of the coil. That reading ran several degrees warmer than the coil itself. The board took it to mean the coil had reached set temperature and stopped the compressor. With the compressor off, the air warmed a little, the reading rose further, and the board restarted. That loop produced the rapid on-off pattern the client described.
What fixed it
We pushed the temperature sensor back into its clip on the coil surface. The clip was intact, so the probe only needed reseating. We then confirmed the sensor reading matched the contact thermometer on the coil within one degree. With the unit reassembled, we ran a full cooling cycle and watched the compressor stay on without cutting out until set temperature was reached. No parts were replaced, and no electronic testing was needed beyond checking the reading.
Outcome
The short cycling stopped at once. The unit ran a full cooling cycle and held its set temperature without cutting off early.
What this case teaches us
A fault that appears right after a service usually traces to the work
- The unit cooled fine before the visit and failed straight after. That timing points to the work done, not a worn-out part.
- A sensor knocked out of its clip reads room air, not coil temperature, so the board cuts the compressor early and the unit short cycles.
- Tell the next technician the service date and what was done. It separates a workmanship slip from a genuine new fault.
Related reading
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