Heating Diagnosis

Component arrangement







Function of individual components

1. Heater/ A/C unit

The heater/ A/C 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 heater/ A/C unit and distributed to the air vents.

1.1 Outside sensor
The outside sensor measures the temperature of the incoming air.

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

2. Heating/air conditioning control
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.

3. Interior sensor
The interior sensor measures the temperature in the passenger compartment.

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

5. Instrument cluster

The instrument cluster provides the following system parameters for control of the heater/air conditioning system:
- Outside temperature (measured below the bumper)
- Coolant temperature
- Speed
- Engine speed
- Time since the ignition was switched off

6. Electric fan with ballast resistor
Fan to cool the condenser.
The ballast resistor serves to reduce the fan speed in the first stage.

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

8. Condenser
The compressed refrigerant is cooled down in the condenser.