Auxiliary Heater Element Relay: Description and Operation

DESCRIPTION





Three relays (1) are used for the electric Positive Temperature Coefficient (PTC) heater unit. The relays are International Standards Organization (ISO) type relay. Relays conforming to the ISO specifications have common physical dimensions, current capacities, terminal functions and patterns (2). The PTC relays are electromechanical devices that switch fused battery current directly to the heating elements of the PTC heater unit as determined by the Powertrain Control Module (PCM).

The three PTC relays are located in the diesel accessory fuse/relay block in the engine compartment.