Temperature Control, Function

Function
The temperature preselected at the temperature selectors is reached or kept constant by:
Heating up by the heater heat exchanger
Heating up by the electric heater booster (on engine 612.963 only)
Cooling down by the evaporator
Cooling down and heating up again (reheat operation)

Heating up
The heater heat exchanger heats up the air flowing past which enters the vehicle interior via the air ducts.

Heating up by the electric heater booster
The heat output of the coolant is insufficient to heat up the fresh air due to the high efficiency of the direct-injection diesel engine. This lack of heat output is compensated by installing the electric heater booster downstream of the heater heat exchanger.

Cooling down
The liquid refrigerant under high pressure is reduced to low pressure via expansion by the expansion valve located on the evaporator. The refrigerant then evaporates. The evaporation heat required for this is removed by the air flowing through the evaporator.
The air which is then cooled down enters the vehicle interior via the air ducts.

Reheat operation
The air which is cooled and dehumidified by the evaporator is heated up again by the heater heat exchanger (reheat).
This prevents the windows misting up from inside.