The A/C compressor coil (or field coil) is an electromagnet. When you turn on the A/C, 12-volt power flows through the coil. This creates a strong magnetic field. The magnetism pulls the compressor clutch hub forward, locking it against the spinning accessory pulley. This drives the compressor pump. Over time, the coil's internal wiring can break or short out from engine heat, disabling the A/C.
Mechanic Glossary
A/C Compressor Coil
The electromagnetic coil that pulls the clutch plate into contact with the spinning pulley to engage the A/C compressor.
Frequently Asked Questions
Use a multimeter to measure resistance across the coil's electrical pins. A reading of 3 to 4 ohms is typical. Infinite resistance indicates a broken wire.
You can replace just the coil. You must remove the compressor clutch plate and pulley to slide the old coil off the snout.
Excessive heat from a slipping clutch plate, or a voltage spike in the electrical system.