Operation

OPERATION

The positive temperature coefficient (PTC) heater unit dissipates 1 kW of electrical power through 3 heating bars. The diesel engine control module (ECM) controls the three relays for the PTC heater unit. The PTC heater unit is split into three "banks". Control logic calls for all PTC heaters to be on all of the time, however, due to limitations in electrical power some of the elements may be turned off occasionally based on alternator load. This allows for lower in-rush current and optimum battery charging. 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, FCM and heating-A/C system. Run the calibration procedure to verify that the concern is not a heating-A/C system issue Heating-A/C System Diagnostics.

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