Aircon Shutting off Mid-Cycle: Temperature Sensor Gone Bad

An aircon shuts off part way through a cycle with nothing visibly wrong. When behaviour is the only symptom, what to suspect.

By Team Snowflake | Updated 24 Aug 2026

Teaching case based on recurring Snowflake service patterns; identifying details are combined.

How this presents

A unit reporting a fault and running oddly, cooling in bursts and stopping short of the setting. Nothing mechanical is obstructed and airflow is normal on both sides. The refrigerant charge measures correct.

Setup: Daikin Wall-mounted4-6 yearsCondoClementi
Misread as: Failure of the control electronics, since the fault shows in behaviour rather than in any visible part.
Check first: The system's own reported temperature compared against a direct measurement

What else produces this

When the mechanical side checks out and the system is still behaving strangely, the question becomes what the system thinks is happening. A sensor is the only place where the machine's picture of reality can differ from reality, and comparing what a sensor reports against an independent measurement of the same thing is a short test. Where the two disagree, everything the system has done since becomes explicable.

A correct charge and clear airflow remove the mechanical explanations for erratic running.
Pipe temperature reported by the system disagreeing with a direct measurement identifies the drift.
Behaviour consistent with the reported figure rather than the real one shows the controls are working correctly.
No fault in the wiring or the board itself keeps the problem at the sensor rather than beyond it in the controls.

Why it happens

Sensing elements change their electrical characteristics with heat, and the controller converts that into a number. Ageing, moisture and corrosion at the connection shift the relationship gradually, so the number drifts away from the truth without the part failing outright. Nothing reports an error, because a wrong number and a right number look identical to a controller. The system then protects and modulates against a temperature that is not there.

What resolution involves

The drifting sensor is replaced and the system behaves normally again, with no change to any other component. The general lesson is about where to look when the mechanics are sound: a system doing something inexplicable is usually doing something sensible with bad information. Find the measurement it is acting on before suspecting the part that acts.

How to tell it worked

The new sensor's reading compared against a direct measurement of the same point on the pipe. Agreement between the two is the proof, and how the system behaves afterwards is confirmation rather than evidence.

Before you approve a quote

A sensor that drifts never reports a fault

A drifted sensor reports no error, because a wrong number looks like a right one to a controller.
Compare what the system reports against a direct measurement of the same point. Disagreement is the fault.
Odd behaviour with sound mechanics means bad information. Find the measurement before blaming the board.

Questions this case answers

Aircon cools well then shuts off after ten minutes: what causes that?

A temperature sensor that has drifted out of accuracy, so the controller acts on a false reading and protects against a temperature that is not there. Nothing reports an error, because a drifted sensor still produces a plausible number.

Does a C4 code on a Daikin mean the control board is dead?

Not necessarily. The board may be interpreting its inputs correctly while the input itself is wrong; read what the system reports for that point, then measure the same point independently, and a meaningful gap identifies the sensor without any dismantling.

Do I need a gas top-up if the aircon keeps cutting out mid-cycle?

No. In this case the refrigerant charge measured correct, and the mid-cycle cutting out traced to a temperature sensor that had drifted out of accuracy rather than a shortage of gas.

How is a temperature sensor checked before a board is quoted?

By comparing what the system reports for that point against a direct measurement of the same point. A meaningful gap between the two identifies the drifting sensor without any dismantling, and a sound board is left alone.

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Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

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