The air tank for the pneumatic control system (PRS) must be discharged for the purpose of replacing components (pressure sensors, valves) in BMW Hydrogen 7 vehicles. After replacing the parts, the tank must be filled from an external compressed air or nitrogen source before the vehicle is started. These tasks can be performed using the present service function.
The requirements for successful execution of these functions are that the engine has been shut down any the vehicle has been parked safely (handbrake engaged). Other information is provided in the program procedure at suitable positions.
Bear in mind the fact that the sequence of the function is always aborted if the engine is started. In this case, the job has not been properly completed and must be repeated. With the engine switched off, the state ”Stand By” is always assumed.
Information for the test step [1] and [2]:
1.) Discharging the pressure accumulator:
In order to be able to start the discharging routine in the program procedure, the sensed tank pressure must lie above 2.3 bar (relative). After discharging, the pressure accumulator must be filled in all cases from an external compressed air or nitrogen source, as otherwise the compressor has to pump a high air volume. This must be avoided at all costs!
2.) Filling the pressure accumulator:
Before running the filling routine, an external compressed-air source must be connected to the supply line of the pneumatic control unit. In doing so, make sure that proportioning valve between the pressure cylinder and PRS in the vehicle is set in such a way that the pressure in the container cannot rise too rapidly.