GF83.20-D-4005H Heater Operating Unit Component Description

GF83.20-D-4005H Heater Operating Unit Component Description

- except CODE (HH9) Regulated air conditioning (Tempmatic)







Shown with code (H13) Additional heat exchanger in load compartment
S98 AAC [KLA] control and operating unit

Location
The comfort AAC control and operating unit is located in the center of the instrument panel.

Task
The vehicle's heater and ventilation are regulated via the AAC [KLA] control and operating unit. On vehicles with code (H13) Additional heat exchanger in load compartment, the rear heater is switched on and off over discrete lines, and the temperature and rate of air flow regulated. The AAC [KLA] control and operating unit communicates via the Controller Area Network bus Class B (interior) (CAN-B) with the following control units:
- With the EIS [EZS] control unit (N73)
- The AAC [KLA] control and operating unit transmits, e.g. "GEBL_EIN (blower motor (M2) activated)"

- With the instrument cluster (A1)
- The AAC [KLA] control and operating unit receives, e.g. "KL_58D_B (Instrument illumination brightness)"

The AAC [KLA] control and operating unit also reads in the following components:
- Fresh air/air recirculation flap actuator motor (M16/21)
- Rear heater water valve potentiometer (A32/1r1), with code (H13) Additional heat exchanger in load compartment

Front temperature selection switch
The blend air and lock-up flap for the front heater heat exchanger can be adjusted mechanically using the front temperature selection switch.
Turning the temperature selection switch to the left reduces the temperature of the air exiting the nozzles, turning it to the right increases the temperature.

Blower switch (S98s1)
The blower switch adjusts the output of the blower motor via the blower motor series resistor group (R14) in the following five stages:
- Stage 0
- Stage 1
- Stage 2
- Stage 3
- Stage 4

Air distribution switch
The air distribution switch is used to adjust the air distribution flaps mechanically. The following positions are possible: defroster vents 12 o'clock position), defroster vents and footwell vents (3:00 o'clock position), footwell vents (6:00 o'clock position), dash support vents 9:00 o'clock position) as well as intermediate positions.

Air recirculation mode button (S98s6)
The air recirculation mode button is used to switch the fresh air or air recirculation mode on or off. Ambient air is sucked into the front heater housing in the fresh air mode over the right air inlet in the engine hood, the particulate filter (for vehicles with code (H81) Ventilation system with filter) and over the fresh air and air recirculation flap. In the air recirculation mode the front heater housing draws in recirculated air from the vehicle interior. In this case, the air is circulated in the vehicle and no fresh air is sucked in. The fresh air and air recirculation flap is adjusted by the fresh air/air recirculation flap actuator motor.
When the air recirculation mode is switched on, the red light emitting diode (LED) in the air recirculation mode button lights up. When the fresh air mode is switched on, the red LED in the air recirculation mode button extinguishes.

Rear air conditioning button (S98s7), with code (H13) Additional heat exchanger in load compartment
The rear air conditioning button is used to switch the rear heater on and off. The rear blower switch (S98s16) then controls the rate of air flow and the temperature of the rear heater is controlled via the rear temperature selection switch (S98s15).
When the rear heater is switched on, the red LED in the rear air conditioning button is illuminated.

Rear blower switch, with code (H13) Additional heat exchanger in load compartment
The rear blower switch regulates the output of the rear heater blower motor (A32/1m1) via the rear heater blower regulator (A32/1a1) to one of the following 3 stages:
- Stage 1
- Stage 2
- Stage 3

Rear temperature selection switch, with code (H13) Additional heat exchanger in load compartment
The rear temperature selection switch is used to determine how the rear heater water valve motor (A32/1m2) regulates the flow of coolant through the rear heater water valve (A32/1y1) to the rear heater heat exchanger. When the rear temperature selector switch is turned to the left, the flow rate is reduced, turning to the right increases it.
To regulate the coolant flow rate, the AAC [KLA] control and operating unit must know the position of the rear heater water valve or the rear heater water valve motor. To do so, the AAC [KLA] control and operating unit reads in the rear heater water valve potentiometer (A32/1r1) over a discrete line.







Design shown with code (H13) Additional heat exchanger in load compartment
98/1 Front temperature selection switch
98/3 Air distribution switch
S98 AAC [KLA] control and operating unit
S98s1 Blower switch
S98s6 Air recirculation mode button
S98s7 Rear air conditioning button
S98s15 Rear temperature selection switch
S98s16 Rear blower switch