Auxiliary Cabin Heater: Testing and Inspection

POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER UNIT

WARNING: Disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions may result in accidental airbag deployment and possible serious or fatal injury

NOTE: See Wiring Information for circuit descriptions and diagrams. Wiring Information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

Prior to replacing the Positive Temperature Coefficient (PTC) heater unit, check the fuses located in the two diesel accessory fuse blocks and check for any Diagnostic Trouble Codes (DTCs) related to the Powertrain Control Module (PCM) and the heating and A/C system and repair as necessary. Initiate the Actuator Calibration function to verify that the concern is not a heating and A/C system calibration issue HVAC Verification Test.

1. Disconnect and isolate the negative battery cable.
2. Disconnect the wire harness connector from the PTC heater unit Cabin Heater - Removal.
3. Using an ohmmeter, check for continuity between each of the terminals of the PTC wire lead connector and the PTC heater ground strap. In each case there should be continuity. If OK, verify the PTC ground strap has a good connection to the body and/or repair the wire harness circuits between the PTC heater unit, Power Distribution Center (PDC) and the PCM. If NOT OK, replace the PTC heater unit.