Aircon Only Trips When It Rains: Water in the Switch Box

A breaker tripping during wet weather and behaving perfectly well when it is dry. The pattern has now repeated across several spells of rain. The unit works without complaint in between them.

Trouble that arrives with the rain and leaves with it is describing water rather than a component. Electrical parts behave the same in any weather unless water is reaching them, so the question becomes where it gets in. That points at the enclosure rather than at anything inside it, and an enclosure is assessed by looking at the box itself rather than by testing what it contains. Nothing inside needs opening until the box has been ruled out.

An outdoor enclosure keeps rain off components that could not survive it, and it does that by staying intact. Rust starts at a scratch, a fixing or an unsealed edge and works through the wall over years. Once there is a breach, water enters during every spell of rain, tracks across whatever it lands on, and produces a trip. The components are doing exactly what they should when wetted.

The enclosure is replaced rather than the contents cleaned, because the contents were never the problem. Cleaning inside a failed box gives a few dry weeks and the next rain repeats it. This is worth saying plainly, because it is where money gets spent twice. The box is a serviceable item with a life, and on any outdoor installation it deserves a look every time somebody is there.