High voltage PTC heater, function

Location
The high voltage PTC heater (N33/7) is located in the front of the engine compartment and it is attached next to the high voltage components above the electric machine (A79/1).

S83.70-A007-76

 Interlock circuit:
The interlock circuit serves to protect people against inadvertent contact with high-voltage components.
All plugs are contact protected.
The seating of all connector couplings is monitored by an interlock circuit.

Function requirements for high voltage PTC heater control unit, general

 Air conditioning system control and operating unit (front & rear AAC) (S98) 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.

The high voltage PTC heater control unit is actuated through a climate control LIN (LIN B8) by the air conditioning system control and operating unit (front AAC &rear AAC), depending on the required 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.

As from a specific operating temperature of the high-voltage batteries, the low temperature circuit 2 is switched-in to the heating circuit and the vehicle interior is then heated by the waste heat of the high-voltage batteries. 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 batteries to be utilized effectively, thereby preserving the energy balance of the high-voltage on-board electrical system.