Automatic window defrosting/defogging (DEFROST, side windows and parked wiper heater) IHKA RR

The regulating element for the automatic window defrosting/defogging is control wheel integrated in the control module/operating unit with 5 diskrete positions. It enables the settings: OFF LOW, MED, HIGH and DEF.

OFF position

In the OFF position, the defrosting flaps are closed. The blower voltage is reduced to the value without the share for the windows.

Blower speed increase

So as not to influence the air volume distribution at the air vents, the blower must be raised or lowered with respect to the position LOW, MED and HIGH by a fixed value. This fixed blower speed increase is stored for all three positions in the control module.

DEFROST function

The DEFROST function is switched on and off via the DEF position of the control wheel for the automatic window defrosting/defogging. On activation of the DEFROST function, fresh-air mode is activated. After subsequent deactivation, the fresh-air mode is only maintained for approx. 5 minutes. The rear compartment blowers are switched off in the DEFROST program.

In order to avoid starting condensation, the defrosting flaps remain closed 12 seconds after the engine is started.

After the DEFROST, the defrosting flaps are moved with a delay into the new flap position.

Side window heating

The side window heating is also activated by means of the control wheel for the automatic window defrosting/defogging. Here, the relay for side window heating is activated as follows:

• HIGH position: clocking 1/1 power (pulse/pause ratio: No clocking)
  
• MED position: clocking 2/3 power (pulse/pause ratio: 80 seconds ON / 40 seconds OFF)
  
• LOW position: clocking 1/3 power (pulse/pause ratio: 40 seconds ON / 80 seconds OFF)
  

At outside temperature < 7°C, the above switch criteria for the side windows are activated; at temperatures > 10°C, they are deactivated.

Wiper rest heating

To prevent the wiper blades from freezing solid, the parked wiper heater heating is switched automatically as a function of the outside temperature:

• Outside temperature < 3°C: activation of heating
  
• Outside temperature > 6°C: deactivation of heating
  

Timing:The first time the parked wiper heater is activated, it is supplied with sustained current for a period stored in the control module. This is followed by a limited period of cyclical operation, with the switch-on phase first. The switching time in cyclical operation mode is a fixed value stored in the control module. So that on average the maximum heat output is not exceeded, the switch-off time is calculated using the heater resistor and voltage at the heating (terminal 30).