Vacuum Supply, Function - GF42.22-P-1004GRH

MODEL 166.063 as of model year 2016 

Function requirements for vacuum supply in general 

• Electronic Stability Program control unit (N30/4) activated through wake-up function
• Circuit 15 ON

Vacuum supply, general 

The vacuum supply for the BAS brake booster (A7/7) is supported by the vacuum pump (M56).

Vacuum supply function sequence 

The Electronic Stability Program control unit evaluates the signal from the brake vacuum sensor (B64/1), which measures the vacuum in the BAS brake booster vacuum chamber.

If the vacuum in the BAS brake booster is too low, the Electronic Stability Program control unit actuates the electrical vacuum pump through the vacuum pump relay (+) (K109) and the vacuum pump relay (-) (K109/1).

If the Electronic Stability Program control unit is activated through the wake-up function and the ignition is switched on, the vacuum pump relay (-) is actuated. The vacuum pump relay (+) is only actuated by the Electronic Stability Program control unit when the vacuum in the BAS brake booster is too low.

As soon as the vacuum, measured by the brake vacuum sensor and assessed by the Electronic Stability Program control unit, reaches the cutoff value, the vacuum pump relay (+) is switched off along with the vacuum pump.

The vacuum pump relay (+) is designed as a solid-state relay, to achieve a faster response time and higher switching frequency. The difference to the vacuum pump relay (-) lies in the fact that mechanical parts are no longer used. A feedback line at the relay output is used by the Electronic Stability Program control unit to monitor the function of the vacuum pump relay (+).