Every Puget Sound heat wave follows the same script: three days of 90°F, and our phone fills with dead ACs — most of them killed by a part that costs less than dinner. The run capacitor is the AC world's weakest link, and knowing its symptoms can save you a few sweaty days of guessing.
What it does, in one sentence
The capacitor stores an electrical jolt that helps the compressor and condenser fan motor start and run efficiently; when it weakens, those motors either strain or never start at all.
The greatest hits of a dying capacitor
The hum-click: the outdoor unit hums for a few seconds, clicks, and gives up — the compressor trying to start without its jolt, then tripping its protector. The stick-start fan: the outdoor fan sits still until you nudge a blade with a stick, then runs — internet-famous "fix" that means the capacitor's fan section is dead and the motor is cooking itself. The late-afternoon quit: cooling that works mornings but dies in afternoon heat; weak capacitors fail hardest when hot. Swollen top: a capacitor with a domed, bulging top has already announced retirement.
Why heat waves harvest them
Capacitors degrade with heat and age — every hour above 90°F ages them fast, and the marginal ones all fail the same week. It's why we stock them by the box every summer and why "my AC died during the heat wave" is usually a modest repair — AC repair with us starts at $285, and a capacitor is one of the quickest jobs in that category — rather than the catastrophe it feels like at 85°F indoors.
The honest warnings
Two things. First, a capacitor stores charge even with power off — it can bite hard; discharging it safely is exactly the kind of two-minute task that's routine for a tech and a bad surprise for a homeowner. Second, capacitors sometimes fail because of a struggling motor or compressor drawing hard; a proper repair includes measuring the motor's draw after replacement so you're not back next month. Swapping the part is easy; confirming why it died is the actual service.
The visit
We carry the common sizes and dual-capacitors in the van, test the old one so you can see the numbers, verify motor amp draw after, and give you a written quote before touching a wire. In a heat wave we triage no-cool calls first — most capacitor jobs have cold air back within the hour.