Air Conditioning (Tempmatic), Function

Function
The electronically controlled cooling/heating and ventilation system if the air conditioning (Tempmatic) keeps the desired interior temperature constant.
AC button pressed (illuminated).
The A/C compressor starts up once the engine has started. If cooling is not required, the output of the A/C compressor is reduced and it is switched off via the anti-icing device.
The air conditioning is always ready for operation once the engine has started and works according to the "Reheat" principle as it is known. This means the A/C compressor always runs above an outside temperature of 1 °C and therefore also cools the inlet air. After the cooling process the dried air is heated up at the heater heat exchanger.
On the one hand this effect serves comfort because cooling down causes the air to dry at the same time, which in turn is an important prerequisite for a pleasant interior climate. On the other hand the air is dried by this cooling down and heating up, preventing the windows from misting up.
Cooling can be switched off by pressing the AC button again (not illuminated).

Cooling operation
The anti-icing device records the temperature at the evaporator air outlet, whilst the in-car temperature sensor measures the respective interior temperature.
The electronic system of the AAC pushbutton control module compares the various measured values with the temperatures set at the temperature selectors and the desired temperature. The microprocessor regulates the air conditioning (Tempmatic) or keeps the respective setting constant as required.

Heater operation
The in-car temperature sensor measures the air temperature in the vehicle interior.
The electronic system of the AAC pushbutton control module compares the interior temperature set at the temperature selectors and the desired temperature.
The electronic system of the air conditioning (Tempmatic) regulates or keeps the respective setting constant as required.

Heater operation with heater booster on vehicles with engine 612.963 as of 12/99
In addition, on vehicles with direct injection diesel engine an electric heater booster is installed in the A/C housing downstream of the heater heat exchanger in order to compensate for the lack of heat output under certain operating conditions.
The 3 heating elements of the heater booster are energized and as a result start to heat up and then to glow. The design ensures that the fresh air drawn in flows straight past the electric heater booster and heats up as a result.