Right-Hand Operating Unit on Rear Climate Control
Right-hand Operating Unit On Rear Climate Control
The right-hand operating unit on the rear climate control is used for individual operation of the rear climate control with left-right separation.
The operating unit regulates the air supply and air temperature (only cooling possible) in the rear via the right-hand roof air vent.
The left-hand operating unit on the rear climate control is connected directly via a plug-in connection to the right-hand operating unit on the rear climate control. This means that all the settings for the left-hand operating unit on the rear climate control are picked up and digitized in the electronics of the right-hand operating unit on the rear climate control.
The right-hand operating unit on the rear climate control consists essentially of the following parts:
- Temperature dial
- Electronic module
- Button for manual variation of the air flow rate
- 5 LEDs (for display of the selected air flow rate)
Functional description
The right-hand operating unit on the rear climate control is activated via the LIN bus by the control module of the automatic rear air conditioning (HKA control module).
The locating lights are controlled via terminal 58g by the footwell module.
The signals of the following components are picked up and digitized in the electronics of the right-hand operating unit on the rear climate control:
- Temperature dial (right-hand operating unit on the rear climate control)
- Temperature dial (left-hand operating unit on the rear climate control)
- Button for manual variation of the air supply (right-hand operating unit on rear climate control)
- Button for manual variation of the air supply (left-hand operating unit on rear climate control)
- Roof air vent temperature sensor, left
- Roof air vent temperature sensor, right
The right-hand operating unit on the rear climate control sends the signals on the LIN bus to the HKA control module.
After signal evaluation, the HKA control module activates the mixed-air flap motors, the air-distribution-flap motors, the LEDs, as well as the fan of the rear climate control by means of an output stage.
Structure and inner circuit
The right-hand operating unit on the rear climate control is connected via a 26-pin plug-in connection to the vehicle network.
Pin assignments
Pin Explanation
Terminal 31L Terminal 31, load ground
Terminal Power supply via wiring harness 30B
Terminal Power supply for left-hand operating unit on rear climate control 30B
SIG Signal line from roof air vent temperature sensor, left
SIG2 Signal line from roof air vent temperature sensor, right
Terminal 31 Terminal 31, ground connection for right-hand roof air vent
Terminal 31L Terminal 31, load ground (ground connection for left-hand operating unit on rear climate control)
LIN LIN bus Terminal 58g Terminal 58g, locating lights (from footwell module)
Terminal 58g Terminal 58g, locating lights (to left-hand roof air vent via left-hand operating unit on the rear climate control)
Terminal 58g Terminal 58g, locating lights (to right-hand roof air vent via right-hand operating unit on the rear climate control)
INT_SIG Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG2 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG3 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG4 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG5 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG6 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG7 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG8 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG9 Internal signal (between right-hand operating unit and left-hand operating unit)
INT_SIG10 Internal signal (between right-hand operating unit and left-hand operating unit)
5 pins not used.
Target values
Observe the following target values for the right-hand operating unit on the rear climate control:
Variable Value
Power supply 12 V
Voltage range 8 to 16 V
Temperature range -40 ± 85 °C
Diagnosis instructions
Failure of the component:
If the right-hand operating unit in the rear climate control fails, the following behaviour is to be expected:
- Failure during operation:
- The current settings are retained.
If only the temperature dial or the button for manual variation of the air flow rate or both components fail, the current settings of the components concerned are retained.
If only the LED display fails, the HKA control module can no longer activate the LEDs to indicate the selected air flow rate.
- No changes are displayed for the buttons and temperature dials in the left-hand or right-hand operating unit of the rear climate control.
- The HKA control module uses a default value for both roof air vent temperature sensors (left and right).
- Fault memory entry in the HKA control module
- Failure is determined on starting:
- The settings on the temperature dials are signalled internally as invalid. The mixed-air flap motors as well as the air-distribution-flap motors are no longer activated. This means the flap motors remain in their parking positions.
The parking position is a certain position to which a flap motor is move after the vehicle has been stopped and parked and after a specified waiting period (stored in the memory chip of the HKA control module). The flap motors are re-initialized to this parking position after starting up.
- The buttons for manual variation of the air flow rate are signalled internal as not pressed. This means the fan for the rear climate control remains off.
- The HKA control module uses a default value for both roof air vent temperature sensors (left and right).
- Fault memory entry in the HKA control module
No liability can be accepted for printing or other faults. Subject to changes of a technical nature