General information
To supply power or control signal to some of the electrical consumers in the vehicle (such as fuel injection components, horn, starter, fan (s) cooling systems, fog lights, etc.) relays are used. In fact, the relay is an electric key that provides the closure of the HV circuit according to the HV signal. In the event of a relay failure, the corresponding consumer fails to function. Most of the relay is placed in mounting blocks located under the instrument panel and in the engine compartment of the car. A description of the check for proper functioning of the relay is given below. Failed relays must be replaced.
Structural diagram of a typical 4-pin relay with terminal and loop numbering
Structural diagram of a typical 5-pin relay with terminal and loop numbering
Examination
1. If it is not possible to find out how the relay is connected to the corresponding electrical circuit according to the wiring diagrams (see Section Wiring diagrams - general information), it should be remembered that the approach to checking any relay is basically the same in all cases (see below).
2. In most relays, a control loop is always connected to two of the contact terminals. When voltage is applied to these LV terminals, the current begins to circulate through the relay control winding, as a result of which the large contacts of the working circuit of the consumer of electricity are closed. The rest of the terminals are the terminals of the working (BB) contour.
3. In order to facilitate the identification of the relay terminals, an explanatory marking is usually applied to its body showing the connection diagram (see illustrations Structural diagram of a typical 4-pin relay with terminal and loop numbering and Structural diagram of a typical 5-pin relay with terminal and loop numbering).
4. Before removing the relay, make sure that the corresponding circuit is de-energized.
5. Connect a fused jumper wire between one of the relay control terminals and the positive battery terminal. Using the second jumper wire, ground the second control terminal - the relay should make a click. Some relays require obligatory observance of the polarity of the connection - if there is no click, try changing the polarity of connecting the control terminals.
6. With jumper wires connected, check for continuity between the BB circuit terminals by connecting an ohmmeter in accordance with the key diagram on the relay housing.
7. If the test fails, replace the relay.
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