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

General information

For giving of power supply or a signal of management on some 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, fog lights and other) relays are used. Actually the relay represents the electric key providing short circuit In/in a contour on a low-voltage signal. In case of a relay exit out of operation there is a refusal of functioning of the corresponding consumer. Relays are installed in the assembly block under the dashboard and in the assembly block in a motive compartment (see an illustration the Block of the relay and safety locks in a motive compartment). The description of check of serviceability of functioning of the relay is given below. The failed relays are subject to replacement.

 The relay block under the dashboard


If it is not possible to find out a way of turning on of the relay in the corresponding electric contour according to schemes of electric connections (schemes are provided in the end of the head), it is necessary to remember that approach to check of any relay in principle is identical in all cases.

In most cases the contour of management is always connected to two of contact plugs of the relay. When giving on these plugs of low-voltage 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 the worker's plugs (In/in) a contour.

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.


  1. Before removal of the relay make sure that the corresponding contour is cut off power.
  2. 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. By means of the second wire crossing point ground the second plug of management, – the relay has to publish click. Some relays demand obligatory respect for polarity of connection, - if the click did not happen, try to change polarity of connection of plugs of management.
  3. At the connected wires crossing points check existence of conductivity between the contour V/V plugs, having connected an ohmmeter according to the key scheme on the relay case.
  4. At negative result of check replace the relay.