Changeover valves, pressure converters
The changeover valves and pressure converters switch the desired partial vacuum to each actuator. The changeover valves and pressure converters are activated by the DDE control unit. On activation, a solenoid valve switches the partial vacuum from the vacuum supply to each actuator.
Changeover valves and pressure converters differ with regard to function as follows:
- Changeover valve:
Switches the partial vacuum either fully off or on. There are no increments between ambient pressure and maximum partial vacuum.
If a changeover valve is not activated, it is sealed to the vacuum supply side.
- Pressure converter:
Can be set steplessly between ambient pressure and maximum partial vacuum.
If a pressure converter is not activated, its is not sealed to the vacuum supply side. A pressure converter causes the vacuum system to lose around 10 mbar per second.
Changeover valve
| 1 | Vacuum output to the partial-vacuum canister |
| 2 | Connection to vacuum supply |
Pressure converter
| 1 | Vacuum output to the partial-vacuum canister |
| 2 | Connection to vacuum supply |
The changeover valves and pressure converters must be checked for the following faults:
- electrical fault
The coil of the solenoid valve and the connections to the plug can have breaks or short circuits.
- Jamming solenoid valve
The solenoid valve can become difficult to move, causing it to jam from time to time. Diagnosing a jamming solenoid valve is a problem, as the jamming often only occurs sporadically. The information under which conditions an actuator does not work must be taken into account.
- Defective vacuum connections
The connections for the vacuum hoses can be broken or burned.
Burned connection.