Cabin Heater - Operation

OPERATION

The Positive Temperature Coefficient (PTC) heater unit dissipates 1 kW of electrical power through four heating bars. The Engine Control Module (ECM) and the Totally Integrated Power module (TIPM) operate the two relays for the PTC heater unit. The PTC heater unit is split into two "banks". Each bank 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. The electrical power output is between 900-1050 W.

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 ECM, TIPM and heating-A/C system. Refer to the appropriate Diagnostic Information.

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