Why does my aircon keep tripping the breaker?
A breaker that keeps tripping is reacting to a real fault: a current leak finding a path to ground, an overcurrent draw on startup, or heat damage at a wiring point. The trip timing tells them apart: immediate, after a brief hum, or alongside a burning smell.
By Team Snowflake | Reviewed 30 May 2026
1. Current leak or short event
The breaker cuts within milliseconds, before the unit ever settles into a run. This happens when electricity takes an unintended path to ground through degraded wiring insulation, moisture-contaminated terminals, or a compressor winding tracking current to its casing. The breaker senses the earth fault and trips. With an RCD fitted, even a tiny leak triggers it.
How to tell
The breaker trips almost instantly, within a second of switch-on. Unlike startup overcurrent, the unit does not hum or strain first, the cut comes before the motor draws any inrush. If the timing repeats identically on every attempt and the unit never reaches a run, insulation testing should come first.
- Breaker trips instantly, before any hum.
- Same trip on every restart attempt.
- Unit never sustains a normal run cycle.
- Trips worsen after rain or in wet weather.
How we confirm it
We shut power first. Then we measure insulation resistance on the compressor and wiring to find the leak path. We replace the damaged section and confirm a safe restart.
Stop resetting the breaker. Each reset drives current through a degraded insulation path and raises the risk of a hard short or arc.
2. Startup overcurrent under load
The unit hums or strains for a moment, then the breaker trips. Every motor draws a surge of current at startup, and the breaker tolerates that brief inrush. When the capacitor weakens or the compressor is stressed, the motor cannot complete its start and draws sustained high current in a locked-rotor condition until protection cuts in.
How to tell
The trip follows a brief hum or strain, the short window where the motor pulls inrush before protection activates. Unlike a current leak, which trips before any sound, the unit was reaching the startup phase first. Check whether the trip lands more consistently on warm days, since heat stress sharpens this pattern.
- Unit hums or strains briefly before the trip.
- Trip lands during the startup surge, not at rest.
- Runtime stays short and unstable between trips.
How we confirm it
We shut power, clamp-meter the startup current draw, and test the capacitor and motor windings to identify the overloaded component before any restart.
Do not force repeated restarts to see if the trip recurs. Each failed start under a weak capacitor accelerates winding damage and can turn a recoverable fault into a compressor replacement.
3. Heat damage at a wiring point
A burning or acrid smell arrives before or with the trip, sometimes with visible scorch marks at a terminal. A connection has overheated under load, or an insulation point has charred through, until the heat or the resulting short forces the breaker open. The smell and discolouration are what set this apart from a clean electrical trip.
How to tell
Heat damage announces itself through smell or visible scorch marks before the breaker cuts. Unlike a silent current leak or a clean startup hum, this trip points to an overheated connection.
- Sharp burning or acrid smell before the trip.
- Scorch marks or discolouration on terminals or wiring.
- Burning smell returns on any restart attempt.
How we confirm it
We shut power first. Then we inspect every terminal and wiring run for burn marks. We test continuity across the suspect joints, replace the damaged section, and confirm a safe restart.
Do not restart if you smell burning. Leave the isolator cut. Each restart can drive an arc or fire at the already-damaged point.
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