MODEL | 909 |
with CODE HH9 (Regulated air conditioning (Tempmatic)) |
N83.10-2156-09
1 | Temperature selection switch | 3 | Air conditioning, heater booster and residual heat rotary switch | A81s2 | Blower knurled wheel switch | ||
2 | Air recirculation mode and air distribution rotary switch | A81 | Climate-control control and operating unit |
Location
The climate control control and operating unit is located in the center of the instrument panel.
Task
The climate control control and operating unit is used to control the heater, air conditioning, ventilation and the residual engine heat utilization system (REST [MRA]) in the vehicle. On vehicles with code (H13) Additional heat exchanger in load compartment, the rear heater is switched on and off and regulated over discrete lines.
The climate control control and operating unit communicates via engine CAN (CAN C) with the following control units:
CDI control unit (N3/21)
– The climate control control and operating unit sends "BLOW_ON (front blower motor (M4) activated)", for example
- The climate control control and operating unit receives "COMP_AOFF (switch off refrigerant compressor (Y38), acceleration)", for example
Instrument cluster (P15)
– The climate control control and operating unit sends "AC_OFF (air conditioning off)", for example
– The climate control control and operating unit receives "KL_58D_B (instrument illumination brightness)", for example
The climate control control and operating unit additionally reads in the following components:
- Refrigerant compressor
– Air outlet temperature sensor (B28)
– Evaporator temperature sensor (B29)
– Outside temperature sensor (B37)
– Refrigerant pressure sensor (B56)
After evaluating the input signals, the climate control control and operating unit actuates the following components over a discrete line:
– Water cycle valve (Y37)
– Circulation pump (M51)
– Additional fan for AC relay (K77), actuation of air conditioning additional fan (M45)
- Refrigerant compressor
– Hot water auxiliary heater control unit (E90), heater booster actuation
– Hot water auxiliary heater control unit (on vehicles with code (H12) Auxiliary heater (hot water))
– Circulation pump (M60) (on vehicles with code (HZ5) Auxiliary water heater 10 kW with timer)
Temperature selection switch
The temperature selector control can be used to set the required temperature in the vehicle interior. When the temperature selector switch is turned down, the air outlet temperature at the nozzles is reduced; turning it upwards increases it. No regulation occurs at the bottom end position and the top end position. Maximum cooling (bottom) or maximum heating (top) is performed. The set specified temperature is compared to the air outlet temperature and regulated accordingly using the water cycle valve.
Blower knurled wheel switch
The blower knurled wheel switch can be used to set the blower output for the front blower motor (M4) using the blower settings 1-3 series resistor (R10) in the following 5 stages:
– Stage 0 (blower "OFF")
– Stage 1
– Stage 2
– Stage 3
– Stage 4 (max. blower output)
Air recirculation mode and air distribution rotary switch
A press of the air recirculation mode and air distribution rotary switch can switch the fresh air or air recirculation mode on and off. In fresh-air mode, ambient air is drawn into the front AC housing over the air inlet above the engine hood, the particulate filter and the fresh air and air recirculation flap.
In air recirculation mode, recirculated air is drawn from the vehicle interior into the front AC housing. In this case, the air is circulated in the vehicle and no fresh air is sucked in. After a period of 10 to 30 min (depending on outside temperature), the system automatically switches back to fresh air mode. The fresh air and air recirculation flap is adjusted by the recirculated air solenoid valve (Y95). If the air recirculation mode is switched on, the LED in the air recirculation mode and air distribution rotary switch lights up. If the fresh air mode is switched on, the LED in the air recirculation mode and air distribution rotary switch goes out.
Turning the air recirculation mode and air distribution rotary switch adjusts the air distribution flaps mechanically using a Bowden cable. The positions for the defrosting vents and the waistrail vents (12o-clock position), waistrail vents and footwell vents (3-o-clock position), footwell vents (6o-clock position), all vents closed (9o-clock position) as well as intermediate positions are possible here.
Air conditioning, heater booster and residual heat rotary switch
At "Circuit 61 ON" (engine running), turning the air conditioning, heater booster and residual heat rotary switch to the 12oclock position switches on the refrigerant /C compressor. When the refrigerant compressor is switched on, the LED next to the "ice crystal" lights up.
At "Circuit 15 OFF" (ignition off), turning the air conditioning, heater booster and residual heat rotary switch to the 6o-clock position switches on the REST [MRA]. The circulation pump and the 1st stage of the front blower motor are actuated. If the REST [MRA] is activated, the LED next to "REST" lights up.
In the 9o-clock position of the air conditioning, heater booster and residual heat rotary switch, the heater booster is activated to achieve speedy heating up of the interior when in deceleration mode or if the engine operating temperature is not reached. The heater booster mode is indicated by the LED under the symbol lighting up.