MSA brief description of components

System circuit diagram

The MSA function is located in the engine electronics (DME/DDE).
Various information from the bus systems is used for the MSA function.
New components are also necessary. The following components for the MSA are described:
· Zero gear sensor
· brake partial vacuum sensor
· MSA button
· Clutch Switch
· Bonnet contact switch
· Belt buckle switch (driver)
· DC/DC converter
· AGM battery

1 brake partial vacuum sensor
2 Zero gear sensor
3 Engine management system (DME/DDE)
4 DC/DC converter
5 Input/output of the DC/DC converter to the distribution box
6 Power distribution box (junction box)
7 Junction Box Electronics
8 Intelligent battery sensor (IBS) at the negative battery terminal
9 Centre console switch centre with MSA button
10 Integrated automatic heating and air conditioning system
11 Instrument cluster
12 Clutch Switch
13 Bonnet contact switch
14 Car Access System
15 Starter motor

Zero gear sensor
The zero gear sensor is fitted at the top of the transmission case and it has the task of detecting the idle position of the gearstick.
Brake partial vacuum sensor
In order to ensure adequate partial vacuum brake power assistance in every situation, the brake booster is equipped with a partial vacuum sensor.
The brake partial vacuum sensor is located beside the brake booster and is connected via a separate cable.

With a brake partial vacuum that is too low, the MSA also starts without activity on the part of the driver. Insufficient brake partial vacuum can lead to safety risks during braking maneuvers. To prevent this, the engine is started.

MSA button
The MSA button (MSA OFF) on the centre console switching centre can be used to deactivate the MSA function. With each terminal change (Terminal 15 On) or repeated pressing of the MSA button, the MSA is reactivated.
Clutch Switch
The present clutch switch is used as an input variable for the MSA to detect clutch operation.
Bonnet contact switch
The bonnet contact switch is included as an influencing factor in the calculation of the MSA. If the engine compartment lid is opened, the engine must not be started or stopped by the MSA function for safety reasons.

In the event of a defective bonnet contact switch, the MSA function is suppressed.
If the bonnet contact switch is pulled upwards, the information (Switch closed) is displayed.
The MSA function is active and an automatic engine start can take place.

Belt buckle switch (driver)
Via the belt buckle switch, the MSA can detect that the driver has fastened his or her seat belt. If the driver has not fastened his or her seat belt, the MSA reacts as follows:
· With the engine running, a switch-off inhibitor is set.
· With MSA stop, the MSA is disabled. A new start is only possible using the START-STOP button.
DC/DC converter
Due to the considerably more frequent occurrence of starting operations, the electrical load that occurs often leads to voltage dips in the vehicle network. In order to stabilize the power supply for certain voltage-sensitive electrical components and thus protect them, a DC/DC converter is used in conjunction with the MSA.
The DC/DC converter supplies the two relays (terminal 30g_DC/DC) and (terminal 30g-f_DC/DC) with a voltage that also remains constant during the starting operation.
The DC/DC converter is fitted in the E-box in the engine compartment.
Via the test leads for input voltage and terminal 50, the electronics decide whether the power is supplied to the output via the bypass or the DC/DC converter.
In the bypass mode, the on-board supply voltage is not fed across the DC/DC converter, rather is transferred directly to the outputs. In the boost mode, there is an adaptation of the on-board supply voltage.
AGM battery
In all cases, the MSA comes with the intelligent alternator control. The much more frequent charge and discharge cycles mean that the load on the battery is very high. The cycle resistance of AGM batteries means that they achieve similar results with regard to service life despite the high load.

In all cases, an AGM battery must be fitted and registered in the vehicle for the MSA to function perfectly.
 

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