Function, individual components

The heating/air-conditioning unit includes:

• Heat exchanger (to heat the air)
• Temperature mixing valve (to control the interior temperature)
• Central valve (to control the air flow)
• Outside air / recirculation valve (to compensate for the dynamic pressure, or recirculation control)
• Fresh-air blower
• Outside sensor (to measure the intake air temperature)
• Blower outlet sensor (to measure the footwell temperature)
• Driver (to control the fresh-air blower speed)
• Evaporator (to cool the air)
• Expansion valve

The outside air is heated or cooled in the heating/air-conditioning unit and distributed to the air vents.

1. 1.1 Outside sensor 

   The outside sensor measures the temperature of the incoming air.

2. 1.2 Blower outlet sensor 

   The blower outlet sensor measures the temperature of air emerging into the footwell.

The heating/air-conditioning control includes the closed and open-loop control electronics, as well as switches for manual influence on automatic program control.

The heating/air-conditioning control regulates the different valves according to the set temperature, the interior temperature, the outside temperature, the vehicle speed and the intensity of sunlight shining into the vehicle.

The interior sensor measures the temperature of the passenger compartment.

The sun sensor measures the intensity of sunlight shining into the vehicle.

The instrument cluster provides the following system parameters for control of the heater/air-conditioning system:

• Outside temperature

  (measured below the bumper)

• Coolant temperature
• Vehicle speed
• Engine speed
• Time since the ignition was switched off

Fan to cool the condenser.

The ballast resistor reduces the fan speed in the first stage.

The air-conditioning compressor sucks the gaseous refrigerant from the evaporator and compresses the refrigerant.

The compressed refrigerant is cooled down in the condenser.