Bad AC Capacitor: Symptoms and What It Costs
A failing capacitor is one of the most common AC faults and one of the cheapest to fix. The classic signs: a humming outdoor unit…
A failing capacitor is one of the most common AC faults and one of the cheapest to fix. The classic signs: a humming outdoor unit that won't start, a fan that needs a nudge to get going, or a system that keeps tripping its breaker.
What it does
The capacitor stores and releases the electrical jolt that gets the compressor and fan motors moving, then helps keep them running. It's a cylinder in the outdoor unit's electrical compartment. Small part, and nothing runs without it.
The symptoms
- Humming but not starting. The motor is getting power but can't turn over.
- The fan needs a push. If it starts after being nudged, that's a textbook failing start capacitor.
- AC blows warm air while the indoor blower keeps running.
- Clicking from the outdoor unit with nothing happening after.
- Frequent breaker trips.
- Visible bulging or leaking on top of the capacitor.
Why they fail here
Heat. Capacitors are rated for a temperature range, and a metal cabinet in full Texas sun in August sits well inside the top of it. Most last five to ten years; in this climate, closer to five. Power surges take out the rest.
Please don't replace it yourself
A capacitor holds a charge after the power is off. It can deliver a serious shock even with the breaker down, and it has to be discharged properly before it's touched.
It's also easy to fit the wrong microfarad rating, which will damage the motor you were trying to save. This is a cheap repair done properly and an expensive one done twice.
Need this looked at in Frisco or nearby? Our diagnostic is $99, credited to the repair, and you get a fixed price before any work starts. See capacitor replacement pricing →
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$99 diagnostic, credited when you go ahead.