Function Vacuum Control
Identification Of Vacuum LinesThe basic color of the vacuum lines for the automatic transmission is black. The lines are identified for the different functions by means of color stripes.
Abbreviated designations in vacuum flow charts:
br = brown
gn = green
rt = red
sw = black
ws = white
Vacuum Flow Chart
At centric connection (VAC) of vacuum transducer full vacuum is engaged with the engine running.
At a coolant temperature of 50°C the switchover valve (125) is connected to ground by means of temperature switch (20). The connection vacuum control valve to connection (VCV) at vacuum transducer is closed. The vacuum generated by the vacuum pump provides a higher vacuum between throttles 63 and 63a than the vacuum controlled at vacuum control valve. This vacuum, which is picked up between the throttles, flows via switchover valve (2-3) to vacuum transducer (connection VCV). As a result, a higher vacuum will be introduced, which results in a lower modulating pressure via connection (TRA) and vacuum capsule on transmission. The temperature switch (20) opens as of approx. 50°C, the ground connection to the switchover valve (125) is interrupted. The controlled vacuum of the vacuum control valve flows through switchover valve (1-3) to vacuum transducer (connection VCV).
Boost Pressure Influence
Independent of coolant temperature the vacuum transducer (connection PRE) will be provided with boost pressure when the turbocharger starts operating. This will result in a reduction of the controlled vacuum (connection PRE) and therefore an increase of the modulating pressure via vacuum capsule on transmission.