The venting procedure must be carried out before any work on the air bellows. The following preconditions must be met before execution of the venting procedure:
The vehicle must be supplied with voltage
Terminal 15 must be on
The vehicle must be on the lifting platform on its own wheels.
Fuse F32 must be removed to prevent control regulation.
The venting procedure activates the drain valve and the two bellows valves of the air supply unit simultaneously for 2 minutes. Depending on the original pressure present in the air bellows, the air escapes more quickly or more slowly. After termination of the venting procedure, the air bellows must be checked by pressing them together. If they can be pressed together, sufficient air has escaped. The air bellows can be removed. If the air bellows are completely filled, the venting procedure must be repeated. The test module provides the possibility to repeat the venting procedure 3 times. After the 3rd time, there must be a pause of 12 minutes so as not to damage the valves by overheating them.
If the air bellows cannot be vented, this can have the following causes:
- A fault code memory entry prevents valve activation
- The original pressure in the air bellows was too low
- The valves or pneumatic lines are soiled.
In these cases, first remedy the fault and then repeat the venting procedure.