Unusual sounds but system still operates. Loose parts, drain, or filter.
The capacitor provides the electrical 'kick' needed to start the compressor; without it, the motor won't turn.
A dirty filter restricts airflow, putting strain on the blower motor and reducing efficiency.
Algae and dust can block the drain, causing water to back up and trip safety switches.
Gaps in the ductwork allow conditioned air to escape into unconditioned spaces like attics.