How do I know if my air conditioner's capacitor has failed?
A failed capacitor shows up as the fan running while the outdoor unit refuses to start — often with a short hum and then silence. The part itself is inexpensive and quick to change, but it must be done by a technician: a capacitor holds a dangerous electrical charge for hours after the power is disconnected.
Do not open the outdoor unit or attempt to replace a capacitor yourself. Capacitors retain a dangerous charge after the power is off, and contact can be fatal.
How to recognise it
- The indoor fan runs but nothing cools
- A hum or buzz from the outdoor unit without it starting
- The compressor starts and cuts out repeatedly
- Intermittent operation, typically worse on hot days
Common causes
Normal wear
Capacitors degrade over the years. Under Israeli summer load, typical service life runs shorter than the manufacturer's figure.
Extreme heat
An outdoor unit in direct sun or without adequate ventilation wears its capacitor out faster.
Voltage spikes
Repeated outages and surges damage the capacitor and shorten its life.
How we handle it
- 1Metering actual capacitance against the rated value
- 2Confirming the compressor itself isn't also at fault
- 3Discharging safely and fitting a matched replacement
- 4A full operating test afterwards
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