Why is my car AC compressor short cycling?

A car air conditioning compressor typically short cycles—meaning it turns on and off rapidly in quick succession—primarily due to incorrect refrigerant levels, usually a low charge caused by a refrigerant leak. When refrigerant pressure drops below a safe threshold, the low-pressure switch trips to protect the compressor from burning out due to a lack of cooling and lubrication. Conversely, an overcharged system can trigger high-pressure safety switches, causing identical rapid cycling behavior. Other common causes include a faulty pressure transducer, a clogged expansion valve or orifice tube restricting flow, a failing compressor clutch relay, or a blocked condenser fin array that prevents proper heat dissipation. Diagnosing this requires connecting a manifold gauge set to read both high and low side pressures simultaneously to identify whether the system is undercharged, overcharged, or suffering from an electrical or mechanical restriction.