Cabin Heater - Operation

OPERATION

The electric Positive Temperature Coefficient (PTC) heater unit dissipates 1 kW of electrical power through three heating elements. The PTC heater unit is split into three "banks". Each bank (element) is driven separately based on alternator load. This allows for lower in-rush current and optimum battery charging. After a bank has been turned on, another bank can only be turned on 10 seconds after the previous. On average, the PTC banks are not switched more than 25 times for each vehicle start. Electrical power output is between 900-1050 W. The Body Control Module (BCM) operates three relays, located in the Power Distribution Center (PDC), for the PTC heater unit Description and Operation.

The control system for the PTC heater unit is diagnosed using a scan tool. Prior to replacing a PTC heater unit, check for any Diagnostic Trouble Codes (DTCs) related to the A/C heater module and BCM.

The PTC heater unit cannot be adjusted or repaired must be replaced if inoperative or damaged.