Why did my aircon start faulting right after renovation?
Renovation work reaches places aircon installers never go. Drilling, hacking and dust all pass close to the wiring and the drain. The fault usually dates from the works, not from the equipment.
By Team Snowflake | Updated 19 Aug 2026
1. Signal cable rejoined in the wrong order
A communication error that appeared immediately after works, and has been constant since, usually means the cable between indoor and outdoor units was cut and rejoined. Renovation workers strip and twist the ends back together to tidy up. The wires go back in the wrong order, so the units can no longer talk.
How to tell
This path is constant. Unlike a nicked wire, the error is there every single time rather than coming and going. Unlike a dust problem, there is an error code rather than a physical symptom.
- The error appeared immediately after the works, not gradually.
- It shows every time the unit is switched on.
- The indoor unit powers up but the outdoor unit does not respond.
- Hacking or drilling happened along the trunking route.
How we confirm it
We open the joint made during the works and check each conductor against the terminal it belongs to. The cable is then reterminated correctly and the units restarted together.
Do not let anyone replace a board for this before the joint is opened. A miswired rejoin gives the same error as a failed board, and the new part will report exactly the same fault.
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2. Communication wire nicked but not cut through
An error that comes and goes after renovation work points to a wire damaged rather than severed. A drill or blade grazing the trunking route can nick the insulation and part of the conductor. The signal still passes most of the time, so the fault appears intermittently and clears on a restart.
How to tell
This path is intermittent. Unlike a rejoined cable, the units communicate most of the time and the error clears on a restart. Unlike a dust problem, nothing is leaking or blowing weakly.
- The error comes and goes rather than showing constantly.
- Restarting the unit clears it for a while.
- The trunking route passed close to recent work.
- The damage is not visible from outside the trunking.
How we confirm it
We test continuity along the disturbed route to find where the signal weakens. That section is then replaced rather than joined, so the repair does not leave a second weak point.
Do not accept a reset as the answer to an intermittent error. The reset clears the code and leaves the damaged conductor in place, so the fault comes back.
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3. Renovation dust in the drain or on the coil
Leaking or weak airflow after works, with no error code at all, usually means fine dust got into the system. Renovation dust is much finer than household dust and passes straight through a filter. In the drain it mixes with moisture into a choke. On the coil it blankets the fins.
How to tell
This path shows no error code. Unlike either wiring fault, the electronics are fine and the symptom is physical, a leak or weak air. The trigger is airborne dust rather than a damaged conductor.
- There is no error code, just leaking or weak airflow.
- Fine dust settled everywhere during the works.
- The unit ran while the renovation was in progress.
- Cooling dropped off around the same time.
How we confirm it
We clear the drain path and assess how far dust has loaded the coil. The coil is then cleaned to the depth the loading actually warrants rather than wiped at the face.
Never leave the aircon running while hacking or sanding is happening. The unit pulls that dust straight onto the coil, which is what causes this in the first place.
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