Mercedes of the S-class W202

1993-2000 of release

Repair and operation of the car



Mercedes W202
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. System of ignition
+ 8. Fuel system
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
- 14. Electric equipment
   14.1.2. Measuring devices
   14.1.3. Technology of measurements
   14.1.4. Checks of electric equipment
   14.1.5. Sound signal
   14.1.6. Replacements of safety locks
   + 14.1.7. Rechargeable battery
   + 14.1.8. Generator
   + 14.1.9. Starter
   14.1.10. Traction relay
   + 14.1.11. System of lighting
   14.1.12. Devices
   14.1.13. Dashboard
   14.1.14. Glow lamps on the dashboard
   14.1.15. Light switch
   14.1.16. Radio receiver
   + 14.1.17. Antenna
   14.1.18. Loudspeakers
   + 14.1.19. Rubber brushes of screen wipers
   14.1.20. Windscreen washer jets
   14.1.21. The washing nozzles of headlights
   14.1.22. Screen wiper and its engine
   14.1.23. Protect the car
   14.1.24. Anticreeping "immunodeficiency"
   14.1.25. Why headlights grow dull
   14.1.26. Galogenka
+ 14.2. Electrical circuitries






14.1.4. Checks of electric equipment

GENERAL INFORMATION

At search of malfunctions in electric equipment system approach is important. It is fair both when checking of the failed glow lamps, and in case of idle electric motors.

The first step is always check of a safety lock as it protects an electric element of a design. The actual arrangement of safety locks can be seen on the napechatka who is on a cover of the block of safety locks.

If necessary replace a faulty safety lock and after connection of the electric consumer check whether it fused again. In this case first of all it is necessary to find malfunction and to eliminate it, here, as a rule, it is about short circuit.

Second control step: If at a serviceable safety lock the glow lamp does not shine, or, respectively, the electric motor does not work, then it is necessary to check a power supply system.

Check of the glow lamp

Take and examine a lamp. If filament or a glass cylinder fused it is weakened sits in a socle, then the lamp should be replaced.

To define whether the glow lamp is serviceable, arrive as follows:

Connect directly to poles of the rechargeable battery a positive wire (+) and grounding (on the car case) a wire (–) and connect them to a lamp. At the same time it is not important what wires are connected to a lamp. Attach one wire to the current distributor, another – to the glow lamp case. If now the lamp does not shine, replace it.

It is necessary to be sure that contacts on a lamp and the lamp boss are not covered with corrosion. If necessary smooth out the correlated or curved conclusions a grinding skin and make normal contact.

If the lamp is serviceable, insert it and include. If the lamp does not shine, then by means of a control bulb check giving of power supply. For this purpose connect a control bulb to the mass of the car. I.e., one wire of a control bulb has to be connected to a good point of the case on the engine (the polished metal) or directly to a negative pole of the rechargeable battery. (+) you hold other probe of a control bulb or on the current carrying plug, or connect it to the wire which is energized. If now the control bulb lights up, and the lamp nevertheless does not burn, then the line connecting the car case to the glow lamp is broken off. That to check it, apply the auxiliary wire connected to the car case to the boss of a lamp. Now the glow lamp has to light up.

Instruction: there are lamps which are equipped only with one feeding line which is energized, for example, parking fire, internal lighting of the car. These lamps by means of the case are directly connected with the mass of the vehicle.

If in a current carrying wire to a lamp there is no tension and the control bulb does not shine, then it is very probable that the switch is faulty. Check the switch for passing of current.

Check of electric motors

In the car escalating comfortableness is provided with low-power electric motors. To them the window regulator, the moved roof panel, system of locks of doors treat with the central management or the electric antenna, for example. At need each electric motor turns on by means of one switch usually manually. In case of the electric antenna the switch automatically is operated via the radio receiver.

Check resistance of the corresponding electric motor, if necessary replace it.


Prevention

Before new actuating remove the cause of an overload of the power window and system of locks with the central management. It can be, for example, the chilled glasses and locks or the polluted fillets of the lowered glass.


If the safety lock at once again fuses, then it demonstrates existence of short circuit.

Unambiguously to find out whether there is a malfunction in the engine, lay two auxiliary wires with a diameter about 2 mm directly from the rechargeable battery of the car to the electric motor. Connect a positive wire to a positive pole, and, the wire connected to the case, to the grounding pole. In case of doubt distribution of poles is defined from the schematic diagram of electric equipment. If it is necessary, for this purpose it is necessary to disassemble the electric motor. All electric motors in the car are powered by the onboard tension (from 12 to 14 Volts). If now the electric motor works normally, the power supply system was faulty.


Prevention

The electric motor which is too slowly rotating or working with interruptions can mean that the sliding electrographite contacts are worn-out. In that case replace these contacts.


If the engine works, then according to the scheme of electric equipment establish what feeding wire brings tension to the electric motor when the switch at earlier included ignition is put in action.

By means of a control bulb check the wire which is energized in the electric motor. As in electric motors big current proceeds, it is possible to replace a usual control bulb with the glow lamp. These lamps are equipped with peaked test needles by means of which it is possible to puncture a connecting wire. Such easy way it is possible to check tension. Engines which alternately rotate to the left / to the right, for example, engines of window regulators have two plus conclusions.


Prevention

Check the screen wiper engine.


If on the electric motor tension does not arrive, then the power supply system is faulty; find defect in the bringing line according to the schematic diagram of electric equipment and eliminate it. As a rule, because of high consumption of current, electric motors have the additional switching relay.

If malfunction is not found, check the switch.

If the wire is damaged, then it is often more rational to lay a new wire as under isolation it is difficult to define the place of a gap.

Check of switches on passing of current

Most of electric consumers join and switched off by means of manually the pressed switch. Besides, there are switches, with the automatic drive. Treat such switches, for example, the switch with a hydraulic actuator (the pressure drop sensor in the brake system) and the sensor of level of brake fluid.

In principle, the switch has a task to close or break off an electric chain. There are switches which break off the grounding line, and switches which break off the line of a positive pole.

Check of switches of lamps and electric motors

Remove the corresponding switch.

Simple switches have only two conclusions for connection of a wire. In this case on one conclusion tension (+), and after inclusion / switching off – and on other conclusion has to arrive. There are switches with several plugs. At these switches on the basis of the schematic diagram it is explained to what plug tension has to be applied. If necessary in advance include ignition.

Check by means of a control bulb whether tension on the switch arrives. If the control bulb lights up, turn on the switch and check whether also tension arrives on the output plug. If this is so, then is established that the switch functions.

If on the output plug there is no tension, then it means that in a wire of giving of power supply there is a gap. On the basis of the schematic diagram of electric equipment check a supply of tension and, if necessary, lay a new wire.

Check of switches sensors

Switches sensors, for example, are the switch with a hydraulic actuator, sensors of level of brake and cooling liquid.

Connect a sampler (a control lamp or an ohmmeter) to the bringing and taking away switch wire, for this purpose remove a wire from the switch.


Prevention

Switches which are screwed in in the block of cylinders of the engine have, as a rule, no wire connecting them to the case as the switch case on top of the block of cylinders of the engine serves as the grounding pole.


The switched-on switch the sampler has to display "passing of current". The best sampler is the ohmmeter: at the switched-on switch it shows zero Ohms, and at switched off – infinity.

Most quicker approximately it is possible to check precautionary switches of level of the cooling and brake fluid, delaying at the included ignition the bringing wire from the switch and pressing it to well grounded place, for example, to the block of cylinders of the engine. If the alarm bulb on the dashboard works, then malfunction is in the switch. The special case represents the switch with a hydraulic actuator (the power failure sensor in the brake system): at an engine stop the contact is closed (the alarm bulb burns), the switch is disconnected only with a certain pressure of oil.

Check of the relay

In many electric chains the relay is installed. The switching relay works as the switch. Example: if driving beam of headlights by means of the manual switch is turned on, then the relay receives the command to switch current to driving beam of headlights. Of course, it would be possible current and directly a tax from the rechargeable battery, by means of light switch. But at all elements with high consumption of current (the high beam headlamp, a screen wiper, a fog light) in a chain the relay is connected not to overload the switch, providing shorter ways of passing of current, Near these combinational relays also functional relays, for example, for systems of a stekloochishcheniye and stekloomyvaniye or the precautionary sound relay for the included external lighting are located.

Check of the switching relay

At inclusion of a lighting element the relay is started, i.e. by means of switching current the electromagnetic coil involves inside contact of the relay and thus closes an electric chain of "working current". Working current via the relay arrives further to the consumer. Most simply operability of the relay can be checked, having replaced it serviceable. Act even in auto repair shop this way. As the owner of the car seldom has at once on hand a new relay, in such cases it is recommended to perform the following operation in case of so-called, switching relays which are used, including, to inclusion of fog and main lights. The marking of plugs specified here, first of all, at serially installed relays, can be presented and in a different way.

Get the relay from the holder.

Include ignition and the corresponding switch.

At first establish by means of tension indicator whether tension on the plug 30 arrives (+) in the holder of the relay. For this purpose connect tension indicator to the case (–), and carefully enter other contact into the plug 30. If the light-emitting diode flashes, then tension is. If the indicator of tension does not show tension, then according to the schematic electrical circuitry find break of the wire going from a positive pole of the rechargeable battery (+) to the plug 30.

Make a conducting crossing point of a piece of the isolated wire, having smoothed out it to gloss.

By means of this crossing point in the holder of the relay connect the plug 30 (+ the rechargeable battery always is energized) to an exit of the closing contact on the plug 87. By means of this working operation the same is practically carried out, as at installation of the serviceable relay.

If with a crossing point, for example, driving beam lights up, then it is possible to consider that the relay is faulty

If driving beam does not light up, find out, whether as it should be connection on the case from headlights. In this case find and eliminate a gap in the line from the plug 87 to the main headlight, using the scheme of connections. If it is required, install the new relay.


Prevention

If defect in an electric chain which is equipped with one relay is shown only periodically, then in this case, as a rule, malfunction is put into the relay: the contact vanishes in the relay or the contact too sticks while in the rest of the time of the relay functions normally. At defect manifestation slightly knock on the relay case. If after this relay switches, replace it.


Check of the engine of a screen wiper

The engine of a screen wiper is installed in a catchment basin, under a windshield. For check it is necessary to remove the corresponding casing.

Marking of plugs

Plugs on the engine are standardly designated as follows:

 – the plug 31 is a plug for connection with the case (in general in electric equipment of vehicles);
 – the plug 53 – receives tension for the first speed of a screen wiper;
 – the plug 53a – delivers positive current (+) for installation in a starting position of brushes of a screen wiper: the engine receives tension through the sliding contact until then while screen wipers work in a starting position if the driver switches off screen wipers;
 – the plug 53v – gives tension for the second speed of a screen wiper (a parallel winding);
 – by means of the plug 53e the screen wiper engine at the movement is stopped back after shutdown in order that screen wipers did not find the stopping way out;
 – the plug 53c (from the relay) – gives tension on the electric pump of a screen wiper.

Check of the engine of a screen wiper

For a start find out whether the engine of a screen wiper and whether as it should be system of electroproviding is serviceable. For clarification of it arrive as follows:

 – disconnect the multicontact shtekkerny socket from the screen wiper engine;
 – by means of two auxiliary wires give tension (+) and weight(s) from the rechargeable battery on the screen wiper engine;
 – lay one wire from a positive pole of the rechargeable battery to the plug 53 or 53v;
 – carry out the second wire from a negative pole of the rechargeable battery to the plug of 31 engines;
 – now depending on the used plug the engine has to work at a step of I or II. If the engine does not work, then it is faulty or its corresponding step. Remove the screen wiper engine.

Check of the device of the blinking light signals

Steps for the device of the blinking light signals and system of the alarm light system are developed by the relay, the so-called sensor of flashing light signals. The system of the alarm light system is connected to the relay without safety lock. The system of the indication of turns is protected by the safety lock which is in the block of safety locks.

If a rhythm of the blinking device quicker on one party, than on another, then on the "bystry" party the glow lamp is faulty or there is a break of a chain.

At emergence of other defects in most cases the breaker of indexes of turns (the sensor of flashing light signals) is the reason.

On the breaker of indexes of turn the following positions of plugs are specified:

 – the plug 31 is the mass of the car (minus in electric equipment of all vehicles);
 – the plug 49 – a relay entrance (the plus tension constantly moves);
 – the plug 49a – a relay exit;
 – the plug C conducts to a control bulb on the dashboard, in the presence of the towing device there can be an additional C2 plug for the alarm system of inclusion of indexes of turn of the trailer.

If you have no new relay, then carefully insert a thin wire between plugs 49 and 49a in the relay shtekkerny socket.


Prevention

At the same time do not damage sensitive relay contacts. Before insertion bend the ends of a wire that there were no keen edges. Again spread the faulty breaker of indexes of turn. Extend so connecting shanks that it was possible to get the breaker, despite shunting again.


Include ignition. If now the lever of indexes of turn is put in action, then the long time shines the relevant party of the device of the blinking light signals. By means of inclusion and switching off of this device it is possible to create a blinking rhythm.

If, despite shunting, the blinking fire does not shine, then the switch of indexes of turn in the electric bringing line is faulty.

Check of a signal of braking

If the braking signal does not shine, then, first of all, check a safety lock in the block of safety locks.

If a safety lock as it should be, check braking signal glow lamps, if necessary replace the fused lamps.

If glow lamps are serviceable, check the braking signal switch which is installed from above to a brake pedal on its rack. At a nazhimaniye on a pedal of a brake press the pin is pulled out from the switch. The contact of the switch becomes isolated and the braking signal lights up.

Check the braking signal switch. For this purpose remove the protection cover from above of a pedal. Remove a tip of wires from the braking signal switch.

Switch off ignition.

Zashuntiruyte both contacts in a tip of wires of the switch of a signal of braking by a short auxiliary wire. If now braking signals light up, then the switch of a signal of braking is faulty and it needs to be replaced.

Check of a heater of back glass

At inclusion of a heating system of back glass after some time the area with visible paths has to be freed from a raid or ice.

At malfunctions at first check a safety lock in the block of safety locks.

If the safety lock is serviceable, check hard landing of a tip of wires turn it to the left and to the right on back glass, if necessary clear it of corrosion products.

If nevertheless the heating system of back glass does not function, check integrity of the bringing wires and operability of the switch, and also the switching relay.

If heating lines are broken off, then for restoration of their connection the conducting silver varnish helps. For this purpose clear the damaged zone a thinner or ethyl alcohol.

On both sides paste over the broken-off place with an adhesive tape and put with a small brush a silver varnish.

Leave a varnish to dry at a temperature about +25 degrees during 24 h. It is possible to warm up it hot air. At a temperature of 130 °C the varnish dries approximately in 30 minutes.


Prevention

Do not include a heating system of back glass until the varnish dries completely. Do not apply gasoline or other solvent to cleaning of the damaged part.