If the A/C clutch on a 1995-’99 Toyota Avalon 3.0L won’t engage and the A/C switch light is flashing, the A/C amplifier senses a difference in engine speed and A/C compressor speed because of a fault in the system. This causes the amplifier to shut off the compressor and flashes the A/C light.

Make sure the compressor drive belt is tight, the clutch is not slipping and the system is properly charged. Check the wiring and connections to the rev sensor, which is located on either the side or the end of the compressor.

Leaving the rev sensor connected, engage the compressor manually and check the AC output voltage of the sensor using an accurate DVOM. It produces about 0.026 volts AC at idle and rises with engine speed to about 0.050 volts AC at 3,000 rpm. If there is no voltage output, then either the sensor is faulty or the magnet in the compressor has fallen off.

See a repair manual for the sensor resistance value. If the sensor needs to be replaced, the system must be discharged before removal.

Technical service bulletin courtesy of IDENTIFIX.

For additional tech tips, visit www.identifix.com.