A/C Signal: Testing and Inspection

Motronic ECU Harness Connector (pin # Locations):

The A/C control unit signals the ECU when the air conditioning is turned on by applying battery voltage to terminal #33 of ECU.

1. Disconnect ECU harness connector from ECU.

2. Turn ignition "ON", and check voltage between ECU connector terminals #33 and #35 (ground). There should be no voltage present.

2. Turn A/C on. Compressor clutch should energize and voltage at terminal #33 should change to battery voltage (within 1 volt). If not, check for open or grounded circuit between ECU terminal #33 and A/C control unit terminal 1/87a.