GF32.22-P-4005RT Level Adjustment, Function
GF32.22-P-4005RT Level adjustment, function
- with CODE (489) Airmatic (air suspension with level adjustment and adaptive damping system ADS)
- up to model year 08
The AIRmatic at front and rear axle is a fully load-bearing suspension system. It keeps the vehicle level constant when the engine is running irrespective of the load. This is achieved by the air compressor pumping air through the AIRmatic valve unit (Y36) into the suspension struts until the vehicle level has stabilized. The vehicle level is determined by two level sensors at the front axle, and one at the rear axle respectively and sent to the AIRmatic with ADS control unit (N51). The adjustment of the level at the individual suspension struts is controlled by the AIRmatic valve unit. A central reservoir for compressed air permits regulation of the vehicle level even when at a standstill. Moreover, the adjustment of the vehicle level is decoupled from the air compressor.
Locking position, function
To ensure that when intentionally raising the vehicle, e.g. using a vehicle jack, that the suspension struts are not continually deflated, it is necessary to automatically detect any wheel-load reduction and to then initiate a locking position. The locking position prevents actuation of the AIRmatic valve unit. If the AIRmatic with ADS control unit sets the locking position, nothing is displayed in the instrument cluster (A1) and any error is not saved. The locking position is automatically canceled by the AIRmatic with ADS control unit under specific conditions (including wheel speed > 0 km/h or 0 mph), and actuator of the level adjustment switch (N72/1s2) and then the level adjustment function returns to operation. Output stage actuations via the diagnosis are then performed independently of the locking position status, i.e. they are always possible.
Normal function (engine runs)
When stationary, the level is automatically readjusted after opening a door or a rear-end door in the event of a deviation.
The level is balanced every t = 180 s while driving.
Depending on the situation, pressure can be produced by the compressor or the pressure reservoir of the central reservoir in order to raise the vehicle.
When the vehicle is stationary pressure from the accumulator is used for noise reasons whereby when raising or lowering the vehicle when stationary only a provisional level is moved to with the target level not being set until the vehicle drives off. When the vehicle is loaded, the lowering of the vehicle level by the level sensors is detected by the AIRmatic with ADS control unit. By activating the solenoid valves, air is delivered to the suspension struts of the front wheel in question or the rear axle until the vehicle level has reached its specified value.
When the vehicle is unloaded the (pressure) relief valve is opened in addition to the actuation of the respective wheel valve.
Wake-up function
With the aid of the microswitches of the rotary tumblers (via the central locking motors), the rear door locking unit (A72) and infrared remote control activity the AIRmatic with ADS control unit is "woken" when the ignition is switched off (circuit 87 = low) by the front SAM control unit (N10) via a hardware line, to check the current vehicle level and to correct it if necessary. The rotary tumbler microswitches and the rear door contact are analyzed by the rear SAM control unit (N10/8) with the result forwarded to the front SAM control unit via CAN-B. When the ignition is switched on the wake-up mode is interrupted by a low/high transition at circuit 61 and the device returns to the normal mode. Level control is performed in the wake-up mode, e.g. following vehicle loading/unloading operations without switching on the compressor. Upon waking up the AIRmatic with ADS control unit, e.g. due to opening a door, a time advance arises which is used for immediate correction to the vehicle level.
Lifting the vehicle is not possible using the level control switch.
Function in the case of vehicle status "ignition ON"
Same function as for wake-up function, but without time limit.
Engine-off function (function duration approx. 1 min)
After "ignition OFF" the control unit records level changes in order to be able to regulate the vehicle level in the event of any loading or unloading processes (raising or lowering) (the same function as with wake up function).
