Mercedes S-Class W-140

In 1991-1999 editions

Repair and enterprise of the car


Mercedes S-Class
+ Mercedes Benz cars of the class S (W-140)
+ operation manual
+ Routine maintenance
+ motor
+ cooling systems, heating
+ systems of power supply and edition
+ electric equipment of the motor
+ gear shifting boxes
+ Awtomatitscheckaja transmission
+ connection
+ brake system
+ Aufhängung and management
+ Body
- Electric onboard equipment
   Specifications
   Diagnostics of defects of the electric onboard equipment - the general information
   Check of the electric motor of a screen wiper
   Check of heated back glass
   Compensation of glow lamps
   Electric protection devices
   Device of electric and electronic devices
   Arrangement of electric basic elements of system of the electric equipment of a car body
   + Schematic diagrams of the electric equipment


Diagnostics of defects of the electric onboard equipment - the general information

Procedures and Kodes of diagnostics of control systems of a pipe are considered in the head the electric equipment of the motor.


To structure various switches, the relay, electric motors, protection devices, the melted inserts or breakers a contour which serve the relation on this component, and also the line and electric plugs can have a typical electric contour electrically components, for association of a component with batteries and belong to the mass of a body. For simplification of a task of search of defects of electric contours the end the management schematic diagrams of electric associations (related watch Schematic diagrams of the electric equipment).

Before starting after elimination of defects some electric contours service, study the corresponding scheme attentively at the same time as its functional definition can imagine more distinctly. Narrowing of a defect search circle the same contour is run due to gradual tracing and an exception of normally functioning components usually. At simultaneous accident at once several components or contours the most probable cause of refusal of peregoranije of the corresponding protection device or violation of grounding (various contours in many cases can be closed on the protection device or a clip of weight).

Failures of the electric equipment often clear up with the elementary reasons, such as corrosion of clips, failure of the protection device, combustion of the melted insert or defect of the relay of switching. Make visuale check of a condition of all protection devices, the line and electric plugs a contour before beginning more concrete check of serviceability of its components.

In case of the application for search of defect of diagnostic devices you plan according to the enclosed electric circuits in what points a contour carefully and is necessary to turn on this device for the purpose of the most effective tracing of defect in what sequence.

To number of diagnostic main devices there are testers of electric chains or the voltmeter (it can be used also 12-woltnaja by Lampe-probnik with the offer of connecting pipelines), the part continuity indicator a contour (probnik), reception a bulb, own source of power supply and the offer of connecting pipelines one. Besides, it is necessary always by car the offer of lines for start of the motor of a resource to have a crocodile equipped with clips of type and, it would be desirable, to the breaker a contour which can be used for schuntirowanija and accession of various components of the electric equipment during diagnostics a contour. Define as is even higher before beginning check of a chain by means of the diagnostic equipment, according to schemes of the place of its Anschließens you.

Verification of effort

Verifications of effort are made in case of functioning violation a contour. Connect one of the testera lines of electric chains to a negative pole of the battery, or sasemlennoj to point of a body of the car of century is too good. You include other testera line to a clip of the electric plug the contour preferable is closer to batareje or the protection device. If the control lamp on testere ignites, the effort on this part of a chain is available that serviceability confirms a contour between this clip and the battery. In a similar manner away - acting, you investigate a constant component a contour. Tracing of lack of effort tells about existence of defect between this point a contour and the last is checked earlier (where the effort was present). Mostly the cause of failure is a weakening of electric associations and violation of quality of contacts.

They remember that food on unites a contour of the electric onboard equipment "is served 1 or "2" only in provisions of the ignition key (watch administrative bodies and the equipment of salon of the head extended the operation manual).

Search of short circuit

One of methods of search of short circuit is an extraction of the protection device and accession instead of it of Lampe-probnika or the voltmeter. The effort in a contour has to be absent. the line, Lampe-probnikom observing podergajte. If the lamp begins to blink, there is somewhere in this texture an end on "weight", is perhaps caused from a wipe of isolation of the line. Similar check a contour, inclusive switches can be made for each of components.

Check of serviceability of grounding

This check is made for the purpose of definition of reliability of grounding of a component. Switch off the battery and include one of lines of Lampe-probnika equipped with an independent source of power supply too consciously well sasemlennoj to point. You include other line of a lamp to the tested texture or a clip. If the lamp ignites, grounding as it should be (and vice versa).

Verifications of the leading ability

Check a contour is made for the purpose of tracing of slopes of an electric chain After power off you check it by means of Lampe-probnika, the equipped independent battery. Include the probnika lines in both ends a contour (or in "the powerful end" (+) and it sasemlennoj to point of a body) is good if the control lamp ignites which is absent a slope in a contour. The refusal of the appendix of a lamp demonstrates violation of the leading ability of a chain. In the similar way it is possible to check and serviceability of the switch, probnik to its clips is included. When translating has to ignite the switch in situation "Wkl" Lampe-probnik.

Localization of a slope

At diagnostics of the slope suspected on existence a contour it is complicated optical enough to find the defect reason as audit of clips on existence of corrosion or violation of quality of its contacts is complicated by a type of limitation of access to it (usually clips are closed by a plug body). Strongly or textures of its lines in many cases leads starts of a body of the plug on a sensor to restoration of the leading ability. Do not forget it in attempts of localization of a cause of failure of the suspect on a slope a contour. Unstably arising refusals can have oxidation of clips or violation of quality of contacts from the reason.

Diagnostics of defects of electric chains does not represent strongly solvable task with preservation of distinct idea of it at all that current works to all electric loadings (a lamp, the electric motor, etc.) about the battery after lines with the switches, the relay, protection devices melted by inserts and then comes back to the battery "mass" of the car. Any problems which are connected with failure of the electric equipment can have from the reason only breaks of transfer of battery current on them or its return to them.