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(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 placed in located under the dashboard and in a motive compartment of the car assembly blocks. The description of check of serviceability of functioning of the relay is given below. The failed relays are subject to replacement.


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 (see the Section of the Scheme of electric connections), it is necessary to remember that approach to check of any relay in principle is identical in all cases.

In the majority of the relay the contour of management is always connected to two of contact plugs. 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.

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.
The constructive scheme of the typical 4-contact relay with numbering of plugs and planimetric connections
The constructive scheme of the typical 5-contact relay with numbering of plugs and planimetric connections


  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 VV plugs, having connected an ohmmeter according to the key scheme on the relay case.
  4. At negative result of check replace the relay.