Diagnosis And Testing - HVAC Control Module

The control switch and timer circuit may be tested in the vehicle with or without a DRBIII(R) scan tool.

TESTING WITH THE DRBIII(R) SCAN TOOL

If using the DRBIII(R) scan tool, refer to the proper Body Diagnostic Procedures.

TESTING WITHOUT THE DRBIII(R) SCAN TOOL

1. Remove the control switch from console and do not disconnect control switch (Fig 1 ).
   Fig 1: Identifying HVAC Control Module Connectors

   Courtesy of DAIMLERCHRYSLER CORP.
2. Using a ohmmeter, check leads between Pins 5 and 8 of the 8-way connector. Depress the rear window defogger button and the resistance reading should be 500 to 520 ohms. If not OK, replace HVAC. If OK, check:
   • Rear window relay (EBL)
   • Blown fuse
   • Cut wire
   • Poor ground
   • Poor connection
   • Defective BCM
   • Bulkhead connector inoperative

Refer to Wiring Diagrams for circuit information.