High voltage PTC heater, function

Location
The high voltage PTC heater control unit (N33/7) is located in the front of the engine compartment on the vehicle.

S83.70-A010-76

Function requirements for high voltage PTC heater control unit, general

 Automatic air conditioning (AAC) control unit (N154) activated.

Function of high voltage PTC heater control unit, general

The high voltage PTC heater control unit is used to heat up the coolant in the heating circuit for the vehicle interior.

The continuous-flow water heater operating principle is used to heat up the water for the heating through a PTC heater with a maximum output of 7 kW. The air is then heated up by the heater core for the vehicle interior.

 PTC = Positive temperature coefficient

The high voltage PTC heater control unit is actuated via the climate control LIN (LIN B8) by the automatic air conditioning (AAC) control unit depending on the requested heating output. The heating elements are heated by energizing them. The coolant flowing past the high voltage PTC heater control unit absorbs the heat of the heating elements and is thereby heated up.

The electric additional water pump (M13/15) routes the coolant from the high voltage PTC heater control unit to the heater core thereby enabling the vehicle interior to be heated.

From a certain operating temperature of the high-voltage battery, the low-temperature circuit 2 (coolant circuit of the high-voltage battery) is switched into the heating circuit and the vehicle interior is then heated by the waste heat of the high-voltage battery.

The heating output of the high voltage PTC heater control unit is automatically switched on or off steplessly, as needed. This enables the thermal energy of the high-voltage battery to be utilized effectively, thereby preserving the energy balance of the high-voltage on-board electrical system.