Capacitor

A capacitor is a small cylindrical part that gives the fan and compressor motors the jolt they need to start and keep running. It's one of the most common AC failures in Gulf heat, and a dead one produces exactly the symptoms people dread — a humming outdoor unit that won't start, or cooling that quits on the hottest afternoons. The good news is that it's inexpensive and quick to swap, so it's always worth checking before condemning the compressor.