Ventilation, function

The ventilation system ensures

 windows free from fogging

 fresh air supply for occupants

 even and pleasant temperatures in the cab reached rapidly

Air supply

Depending on whether recirculated mode or normal mode is active, the air is drawn out of the vehicle interior (recirculated air mode) or drawn in via the fresh air intake opening (normal mode) and delivered through the air ducts to the adjusted air outlets.

If fresh air mode is switched on (indicator LED for recirculated air mode is off), the automatic air conditioning (KLA) switches over automatically from normal mode to recirculated air mode if via the air quality sensor an increased pollutant emission is detected.

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The fresh air/recirculated air flap is operated via an actuator motor which is actuated by the automatic air conditioning (KLA) control and operating unit.

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Blower

Depending on the mode the blower draws in air from the vehicle interior or fresh air via the fresh air intake opening and delivers it through the heater blower unit to the air ducts. The air drawn in is routed to the air outlets via the air ducts.

The blower speed and therefore the blower capacity can be influenced automatically or manually in the process depending on the position of the blower switch.

If the blower switch is in the  position, the blower capacity is automatically adapted to the heating or cooling conditions as well as the instantaneous vehicle speed.

As the speed reduces between 80 and 20 km/h and with a changeover from fresh air to recirculated air mode it is raised in order to compensate for the reducing head pressure.

The blower is actuated by a blower regulator in a pulse width modulated manner. Continuous adaptation of the blower capacity is therefore possible at all times. In turn the blower regulator receives the information required for actuation from the automatic air conditioning (KLA) control and operating unit.

 On vehicles with auxiliary heater (ZHE) the blower can be actuated independent of the position of the blower switch.

The actuation ensues when the auxiliary heater (ZHE) is in heat mode.

W83.10-1004-78

Air distribution duct

The arrows show the air distribution and the air outlets available for ventilating the cab.

Temperature-controlled air (red/blue arrows) flows out at all air outlet openings.

The air distribution of the electronic cooling/heating/ventilation system of the automatic air conditioning (KLA) contains:

 a defrost duct with 13 outflow openings along the windshield which are opened or closed via a rotary switch

 two center nozzles, adjustable in all directions in the center part of the instrument system

 new air ducting in the driver and front passenger door:

 a mounted air guidance unit makes it possible to supply air selectively to the respective side window

 outlets on both sides and next to the steering column for the driver footwell

 one air guidance duct for the front passenger footwell

The air is distributed to the air ducts by means of air distribution flaps which are operated by the air distribution actuator motor. Depending on the position of the air distribution switch the air distribution actuator motor is actuated by the automatic air conditioning (KLA) control and operating unit.

If the air distribution switch is in the  position, then the air distribution flaps are adjusted as per a characteristic stored in the control unit, depending on whether the automatic air conditioning (KLA) is in heating or cooling mode.