Aircon contactor
The contactor is a power switch in the outdoor unit. When it fails, the unit may click, hum, or stay silent even when the indoor unit is calling for cooling.
Parts summary
Warning Signs
What it is and where it sits
The contactor is an electrical switch in the outdoor unit. It turns on power to the compressor and fan.
Think of it like a relay that the control board uses to switch power on and off.
When the signal arrives, the switch closes and power flows. If the switch breaks, power never flows.
Failure modes and warning signs
Contactors switch on and off thousands of times. The contacts wear out and stop making good connections.
You notice the indoor unit runs but the outdoor unit stays quiet. No cooling arrives.
Sometimes you hear a click from the outdoor unit but nothing else happens. That is the signal arriving but the switch failing to close.
- Indoor fan runs but outdoor unit is silent
- Clicking sound from outdoor unit but no cooling
- Unit works some times but not other times
How we verify the problem
Technicians first test the capacitor. A weak capacitor looks like a contactor fault.
They then test the contactor with power on and check if the signal arrives. Does it close when signaled?
They look for burn marks or wear on the contact surfaces. Burned contacts show the switch is failing.
| Test Finding | What It Means | Next Step |
|---|---|---|
| Capacitor is weak | Weak capacitor causes no-start | Replace capacitor first |
| Contactor does not close when signaled | Switch is broken | Replace contactor |
| No signal from control board | Board is not sending signal | Check control board |
| Everything works but nothing starts | Compressor may be faulty | Check compressor |
Should you fix it now?
Replace only if testing shows the contactor is broken. Test the capacitor first.
You can wait if the unit works sometimes but not always. But replace it soon because it will likely fail completely.
Do not wait if nothing ever starts. This needs immediate testing.
What to expect
Contactor replacement is quick and cheap once the problem is confirmed.
Testing first saves money by avoiding replacement when the capacitor is really the problem.
An intermittent contactor usually fails completely soon, so early replacement prevents a breakdown on a hot day.
Common questions
Same situation with your aircon?
Describe it on WhatsApp