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Home >> Mercedes Benz >> 2021 >> Metris Van Cargo >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Climate Control System (1 Of 3) -- 447 Chassis >> Basic Knowledge >> Ventilation System, Function - GF83.10-S-2000TRB

Ventilation System, Function - GF83.10-S-2000TRB

Model 447.6/7 

Model 448.7 

G16502044Courtesy of MERCEDES-BENZ USA

Front ventilation function With Code HH4 (THERMOTRONIC automatic climate control) or With Code HH9 (Semi-automatically controlled air conditioning, TEMPMATIC) 

The front ventilation ensures aeration of the front vehicle interior (air circulation) and also ensures the following conditions:

Aeration can occur using one of the following two modes:

Selection of fresh air mode or air recirculation mode is controlled in a code-specific manner using the following buttons. The buttons are integrated in the air conditioning control and operating unit (AAC [KLA] V & AAC [KLA] H) (S98).

  CODE HH4 (THERMOTRONIC automatic climate control) CODE HH9 (Semi-automatically controlled air conditioning, TEMPMATIC)
Air recirculation mode button Air recirculation mode button (S98s7) Air recirculation mode button (S98s7)
Increase air flow button Increase air flow button (S98s5) -
Reduce air flow button Reduce air flow button (S98s13) -
Air flow selector wheel - Air flow selector wheel (S98s19)
"MODE" up button "MODE" up button (S98s6) -
"MODE" down button "MODE" down button (S98s12) -
Windshield air distribution button - Windshield air distribution button (S98s16)
Center air distribution button - Center air distribution button (S98s17)
Footwell air distribution button - Footwell air distribution button (S98s18)

To control the rate of circulation, the different blower setting variants are used to increase or decrease the output of the blower motor (M2) via the blower regulator, as required, in 7 stages. The output of the blower motor can also be increased or decreased automatically via the blower regulator by using the "AUTO" button (S98s2) (with CODE HH4 (THERMOTRONIC automatic climate control)).

The drawn in fresh or recirculated air in the front vehicle interior is then distributed, depending upon the request for air distribution, via the following air outlets:

Fresh air mode 

Fresh air mode is activated if the LED in the air recirculation mode button does not light up. The fresh air/recirculated air flap actuator motor (M2/5) puts the fresh air/recirculated air flap into "Fresh air open" position. In this position, the blower motor draws ambient air into the air conditioner housing via the right engine compartment air inlet grille, the interior air filter and the fresh air/recirculated air flap.

Recirculated air mode 

The air recirculation mode is switched on when the LED in the air recirculation mode button lights up. The fresh air/recirculated air flap actuator motor puts the fresh air/recirculated air flap into "Recirculated air closed" position. In this position, the blower motor draws the recirculated air from the front vehicle interior into the air conditioner housing. Depending on the configuration of the blower setting variants and the temperature selection and air distribution variants, recirculated air passes into the front vehicle interior again through the air ducts and air outlets.

In heating mode, the system switches to fresh air mode. The transition phase (minimal heating/cooling mode), on the other hand, is controlled using variable mixed air. In cooling mode (max cool), the system switches to air recirculation mode. Automatic flushing with fresh air takes place by way of a set time defined in the air conditioning control and operating unit (AAC [KLA] V & AAC [KLA] H).

Rear ventilation function With Code HZ7 (Semi-automatically controlled air conditioning, TEMPMATIC in rear) 

To control the rate of circulation, the different blower setting variants are used to increase or decrease the output of the rear blower motor (A32/4m1) by way of the rear blower regulator (A32/4r1) as required, in 7 stages. The output of the rear blower motor can be automatically increased or decreased via the second menu level using the "AUTO" button (with CODE HH4 (THERMOTRONIC automatic climate control)) or the "REAR" button (S98s9) (with CODE HH9 (Semi-automatically controlled air conditioning, TEMPMATIC)) in the air conditioning control and operating unit (AAC [KLA] V & AAC [KLA] H).

IMPORTANT Air distribution is performed automatically, depending on the setting of the front unit and the operating mode. In automatic mode, the rear unit is set synchronously with the front unit to make sure the ideal thermal comfort is reached in the overall vehicle.

The distribution of the drawn in fresh or recirculated air is carried out via the following air outlets:

Function sequence for actuation of the air ducting flaps 

The air distribution in the vehicle interior is controlled by adjusting the air ducting flaps in the air conditioner housing.

The following air duct flaps are operated:

The air conditioning control and operating unit (AAC [KLA] V & AAC [KLA] H) sends an "actuator motors" request via the climate control LIN 1 to the rear heater/air conditioning air recirculation unit (A32/4), which then directly actuates the actuator motors.

IMPORTANT The fresh air/recirculated air flap is closed after an accident (crash signal sent).

IMPORTANT The defroster/footwell/center air vent/side air vent flaps are operated via a linkage from the air distribution actuator motor.

  Overview of system components for climate control Model 447.6/7
Model 448.7		 GF83.40-S-9994TRB 
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