A/C Pulser System Electrical Diagnosis - 89MY, 90MY Loyale

This information is intended specifically for the above referenced models equipped with either Hitachi or Panasonic A/C systems, however, other models and years using a pulse sensor system may have application as well.

These diagnostic tips will address a condition where upon engine start-up the A/C is turned on and the clutch engages and runs for several seconds only to shut off by itself. The clutch may also become disengaged and stop the compressor from running if the engine is revved up slightly right after engine start-up.

Should you experience a similar condition, and the A/C drive belt's condition and tension has been confirmed as good (important), suspect the A/C pulser system and follow the checks outlined below.

1. Start engine and engage the A/C system.

2. Find the A/C relay located under the hood on the firewall, RH (passenger) side.

3. Ground the red wire with the black tracer or on turbo models the red wire with green tracer, using a wire or test light.

4. If the compressor comes on and stays on, the pulser system is probably at fault.

The components of the pulser system that should be checked are listed below. Refer to the information contained in the appropriate Service Manual to provide specific checking details.

^ Compressor pick-up sensor
^ Evaporator thermostat
^ Loose wires on ignition coil
^ Pulse amplifier
^ Mode panel assembly (provides a ground to evaporator thermostat)

Remember the function of the pulser system is to compare engine speed to compressor speed and to shut off the A/C compressor if the amount of difference exceeds 2O% to 25% and falls into the lock detection range.