Why does my aircon keep tripping the breaker?
An aircon that trips the breaker usually has an electrical fault: old or burnt wiring, a shorted circuit board or fan motor, or a failing compressor. If it trips the moment the power goes on, do not force it back on: that risks an electrical fire. Switch it off at the isolator and have an aircon technician check it.
Key takeaways
- The breaker is protecting you: it trips when current overheats a wire or leaks to earth, so a trip is a warning, not a nuisance.
- An instant trip is serious: tripping the moment the power goes on means the high-voltage electrics or electronics are affected.
- Call an aircon technician first: an electrician handles the power supply but cannot tell whether the aircon can be repaired.
- Three causes cover most of our jobs: loose or burnt wiring, a faulty board or fan motor, and the compressor.
The video above is a real job: a home with four aircon systems where the aircon kept tripping the power. The old three-core main power cable from the isolator to the outdoor unit's power terminal had broken down. We replaced it with a new three-core Keystone 70c cable, closed up the isolators, and the units ran again. Keystone cables are made in Singapore by Keystone Cable, and they are the only cables we use, because they are the brand we trust.
What to do when your aircon trips the breaker
- Switch the aircon off at its isolator. The isolator is the switch on the wall near the indoor or outdoor unit.
- Note when it tripped. The instant the power came on, a few minutes after the aircon started cooling, or during heavy rain. Tell your technician; it saves time.
- Do not switch it back on to test it. If it tripped the instant the power came on, the high-voltage electrics are affected, and forcing it on can start an electrical fire. Stop at once if you smell burning or see scorch marks on a switch.
- Reset the breaker once, only with every aircon off. Do this only if the breaker also serves other things you need. If it still trips with every aircon isolator off, the fault may be in the home's wiring: mention it when you book.
- Book an aircon technician. Keep the aircon off until it has been checked.
Tripping right now? Message Luna on WhatsApp, or book an aircon repair.
What causes an aircon to trip the breaker?
When it trips | What it points to | Who checks it |
|---|---|---|
The instant the power goes on | High-voltage electrics or electronics: burnt or damaged wiring, a shorted board, or a shorted compressor | Aircon technician, at once |
A few minutes after cooling starts | The compressor or outdoor fan motor failing as it starts | Aircon technician |
During or after heavy rain | Water in the isolator, a cable joint or the outdoor unit's electrics | Aircon technician |
Even with every aircon switched off | The home's wiring or the breaker itself | Licensed electrical worker |
1. Loose, burnt or old wiring
This is the cause we find most. A loose connection at the isolator or terminal block heats up each time the aircon runs, until the insulation burns and the current leaks. Power cables to outdoor units also age in Singapore's sun and rain until the insulation breaks down. That was the problem in the video above, and a new cable from the isolator to the outdoor unit ended the trips.
2. A faulty circuit board or fan motor
A board (PCB) or fan motor with a short draws more current than it should, or leaks it to earth, so the breaker cuts out. Fan motors on outdoor units wear out on the ledge, as in our Daikin E7 outdoor fan motor job. Board faults often show a blinking light or error code first; our guide to Daikin blinking lights shows how to read one.
3. The compressor
The compressor is the big motor in the outdoor unit that moves the gas around. A compressor can fail in any system, old or new. Its internal windings can short without anyone noticing, and a compressor installed with bad or no evacuation (pumping the air and moisture out before the gas goes in) degrades and can die long before it should. When a winding shorts or leaks to earth, the breaker trips as the compressor tries to start. After the diagnosis we tell you whether it is worth repairing.
A second case: a Panasonic that tripped its RCCB
In another job (watch the check on YouTube), a Panasonic kept tripping the aircon's RCCB, the safety switch at the DB box that cuts power when current leaks to earth. Our technician started at the DB box, then checked the indoor unit, the gas and the outdoor unit's electrics one by one. The cause was a faulty wiring cable, not a broken aircon part, so we replaced the cable with a new one and no aircon parts were needed. This is why we test before quoting: the most expensive guess is often the wrong one.
Who fixes what?
Call an aircon technician first. An electrician looks after the power supply, but cannot test the aircon's electronics or tell you whether the aircon can be repaired.
Part | Who works on it |
|---|---|
Aircon units, boards, fan motors, compressor | Us |
Isolator and the aircon's power cable to the outdoor unit | Us |
DB box, breakers, RCCB, the home's wiring | A licensed electrical worker |
If we find the fault is on the DB box side, we tell you what we found so your electrician knows where to look. The how an aircon works guide shows where each part sits.
What it costs
Job | Price | What drives it |
|---|---|---|
Power trip diagnosis | S$150 | Testing the wiring, isolator, board, fan motor and compressor to find the real cause |
Power cable replacement (Keystone) | From S$150 | The length of cable from the isolator to the unit |
Isolator replacement | Quoted after the S$150 diagnosis | The isolator and how it is mounted |
Board, fan motor or compressor | Quoted after the S$150 diagnosis | The part for your model |
Repairs carry our warranty from 180 days.
When to call a technician
Call us straight away if the aircon trips the breaker the moment the power goes on, if it trips whenever it rains, or if you smell burning near the isolator or the aircon. Keep it switched off at its isolator until then. You can book online in under a minute, or ask Luna on WhatsApp at any hour.
Frequently asked questions
Is it safe to switch the aircon back on to see if it trips again?
No. If it tripped the instant the power came on, the high-voltage electrics or electronics are affected. Forcing it on again can start an electrical fire. Leave it off at the isolator until it has been checked.
Should I call an electrician or an aircon technician?
An aircon technician first. An electrician looks after the power supply, but cannot test the aircon's electronics or tell you whether the aircon can be repaired. If we find the fault is in the home's wiring, we tell you where it is.
Can a new aircon have a compressor fault?
Yes. A compressor can fail in any system, old or new. Its windings can short without warning, and a compressor installed without proper evacuation wears out much sooner than it should.
Why does my aircon trip only when it rains?
Water may be reaching the isolator, a cable joint or the outdoor unit's electrics. The breaker senses the current leaking to earth and cuts the power. It needs the wet part found and sealed or replaced.
Does your warranty cover the repair?
Yes. Our repairs carry a warranty from 180 days.
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Eric Lim, aka Uncle EricFounder of iAircon.Repair, now in its 10th year servicing aircons in Singapore. Some of our jobs are filmed, and you can watch the work on YouTube.
