11.3. Switches

The switch the electric chain of the corresponding device becomes isolated. In E-class cars Mercedes-Benz used absolutely new generation of switches. All buttons, rotary, mobile, press and other switches are ergonomic and easy to use.
   The combined switch
Management of indexes of turn, a screen wiper and a light signal is carried out by the unique understeering switch on the left side of a steering wheel. In the same place there is a governing body of light: the combined switch of parking, passing and fog beam, back fog lamps, the regulator of the proofreader of headlights.
This switch (the designation "S4" on electrical circuitries) – really difficult mechanism as not less than 12 wires are brought to it and it is commutated variously. Such combined switch was installed also on the former Mercedes models. For years of operation the following problem appeared: in process of wear the switch of indexes of turn ceases to be fixed. In this case the combined switch was subject to replacement. Attempts to finish system of fixing often brought only temporary improvement.
   Combination of devices and switches

Fig. 10.7. Central console


All important switches of management are located on the central console (fig. 10.7). For convenience switches are divided into functional groups:
in the top row there are switches of the drive of back head restraints, the central blocking and the alarm system;
in a middle part are located the control unit of system of heating, the conditioner and the recirculation button;
are the block of switches for management of electrowindow regulators in the lower part of the central console, blocking of doors for protection of children and a key of adjustment of external rear-view mirrors.
Having raised the head, it is possible to see the new control unit of illumination of salon and the movable hatch. There is a ventilated sensor of system of heating and conditioning.
   Electronic system of launch of the engine
The switch of this system — almost most important in the car and too new development. The electronic switch of ignition — the main essence is clear from the name. There is no lock of ignition and the ignition key in traditional understanding in Mercedes of the E-class any more. They were succeeded by difficult electronic system in which the usual mechanical key was replaced by the device with several functions. The main difference of an electronic key — absence metal a small beard: for launch of the engine the wedge-shaped uvula is implanted into a nest of the switch of ignition and turns to the right. All the rest is carried out by electronics. On models with the automatic transmission she carries out the procedure of start before launch of the engine.
However at first in the switch of ignition there takes place the control process occupying fractions of a second during which electronics automatically checks whether the correct key is inserted into the lock. For this purpose the switch gives in the inductive way food to a key which in reply infrared radiation transmits the coded signal. The microprocessor of the switch of ignition verifies a code with the value which is kept in memory and at compliance releases electric blocking of a steering wheel. Now the key can be turned for inclusion of ignition to the right. Codes of an electronic key and the value which is kept in the processor memory at each new start-up are replaced and anew remain in memory.
It is more convenient to carry out an inspection of the switch of ignition from the contact socket under a steering column. On symbols on the switch it is possible to understand what contacts are connected at the relevant provision of a key. At emergence of malfunctions replace the ignition switch with service stations as the helmsman of a column is necessary for its removal and removal the special tool.
   Security system (system of the admission)
Since December, 1994 Mercedes-Benz serially equips all models with security system with electronic control which meets more strict requirements of the law and motor insurers. The main element of new security system is the infrared remote control issued in the form of an electronic door key. The car door has to be open previously for launch of the engine by means of this remote key. Otherwise the control system of the engine will remain blocked and the engine cannot be launched.
The small transmitter in a key radiates the invisible infrared signal combined with a radio signal on several accepting devices located in doors and behind an internal rear-view mirror. The accepted and processed signal is transmitted to the control unit in a motor compartment. There the signal is fixed in memory, the new code which will be necessary for the following (or later) opening of doors and launch of the engine is generated. At the same time there is a data exchange to the control unit of the engine for blocking of start-up and system of the central blocking of locking of doors.
   Switch of the alarm system
The button of the switch of the alarm system at the included lighting poorly is highlighted by a small lamp. So occurs because the lamp receives tension via the resistor. When pressing the button the resistor is switched off from a chain, and the lamp begins to shine in full capacity in the blinking mode.
   Check of switches
If during troubleshooting in electric equipment, it is necessary to check the switch, at first find it on the scheme, and then check its connection. For this purpose it is possible to use or a lamp sampler and to check presence of tension, or an ohmmeter in the removed state. In most cases the first method is more preferable. Check whether it is possible to get a needle of a lamp sampler the checked wire in the contact socket. If is not present, it is possible to puncture with a sting isolation. On-off switches can be removed only after facing dismantle. Other switches of a privernuta. Many switches in the car have internal illumination. Unfortunately, lamps in them are not subject to replacement, except for light switch.

SEQUENCE OF WORKS
1. It is possible to puncture with a needle of a lamp sampler isolation of a wire for verification of tension on them.
2. Have near at hand the corresponding electrical circuitry.
3. At first check whether tension on the switch moves in general. For this purpose it is necessary to include ignition or lighting.
4. Then check whether tension transfers the switch in the relevant provision.
5. On the example of the switch of ignition and a starter an inspection has to be carried out as follows:
– the current carrying red wire from the positive plug of the rechargeable battery always has to be energized;
– on a wire of the 15kh plug of the switch of the lock of ignition there has to be current when the switch is in provisions "I", "II" and inclusions of a starter;
– on a wire of the 15 plug of the switch of the lock of ignition there has to be current when the switch is in provisions "II" and inclusions of a starter;
– on a violet wire of contact "50" current have to go, only when the switch is in the provision of inclusion of a starter.