Mercedes M-Class W163

since 1997 release

Repair and operation of the car

Mercedes W163
+ Mercedes-Benz cars of a class M (W163)
+ Governing bodies and methods of safe operation
+ Current leaving and service
+ Engine
+ Cooling systems, heating and air conditioner
+ A power supply system and production of the fulfilled gases
+ Systems of electric equipment of the engine
+ Manual box of gear shifting
+ Automatic transmission
+ Transmission line
+ Brake and auxiliary systems
+ Suspension bracket and steering
+ Body
- Onboard electric equipment
   General information and precautionary measures
   Search of causes of failures of electric equipment
   Safety locks - the general information
   Chain breakers - the general information
   The relay - the general information and check of serviceability of functioning
   Digital tire of data of CAN
   + Assembly blocks, elements of control systems
   + Dashboard, switches, traveling computer
   + Driving electric motors
   + Alarm and lighting fixtures, sensors of a rain and temperature of external air
   + Systems of additional safety (SRS)
   + Audio system
   + Schemes of electric connections

The relay - the general information and check of serviceability of functioning

General information

For giving of power supply or a signal of management on many of consumers of the electric power in the car (such as components of system of injection of fuel, a horn, a starter, the cooling system fan(s), fog lights and so forth) relays are used. Actually, the relay represents the electric key providing short circuit of VV of a contour on NV to a signal. In case of a relay exit out of operation there is a refusal of functioning of the corresponding consumer. The most part of the relay is located in a motive compartment, others "are scattered" on the car. The description of check of serviceability of functioning of the relay is given below. The failed relays are subject to replacement.



  1. Correctness of connection of the relay can always be determined by Schemes of electric connections.
  2. Usually the contour of management is always connected to two of contact plugs of the relay. When giving on these NV plugs of tension current begins to circulate on a winding of management of the relay therefore there is a short circuit of big contacts of a working contour of the consumer of the electric power. Other plugs are plugs of working (VV) of a contour and become isolated among themselves when giving food on a contour of management.
  3. For the purpose of simplification of identification of plugs of the relay explanatory marking with the image of the scheme of connection of keys is usually applied on its case. If similar marking is absent, it is necessary to address schemes of electric connections.
  4. For check connect an ohmmeter between two VV plugs of a contour of the relay, - in the relay of normally opened type conductivity has to be absent. Now connect the wire crossing point equipped with a safety lock between one of plugs of management of the relay and the positive plug of the battery (In +). By means of other wire crossing point ground the second plug of management, - the relay has to publish click after which the ohmmeter will record conductivity existence (the relay of normally opened type). Some relays demand obligatory respect for polarity of connection.
  5. At negative result of check replace the relay.