Relay — general information and function check

To supply power or control signal to many 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 the engine compartment, others "scattered" by car. A description of the check for proper functioning of the relay is given below. Failed relays must be replaced.

Examination

1. The correct connection of the relay can always be determined by the wiring diagrams given in the last Section of this Chapter.

2. Usually, a control circuit is always connected to two of the contact terminals of the relay. 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) circuit and are closed to each other when power is applied to the control circuit.

3. In order to facilitate the identification of the relay terminals, an explanatory marking is usually applied to its body with an image of the key connection diagram. If there is no such marking, refer to the wiring diagrams (see Section Wiring diagrams).

4. To check, connect an ohmmeter between the two BB terminals of the relay circuit - there should be no conductivity in the relay of the normally open type. Now connect a fused jumper wire between one of the relay control terminals and the positive battery terminal (B+). Using another jumper wire, ground the second control terminal - the relay should make a click, after which the ohmmeter will record the presence of conductivity (normally open relay). Some relays require obligatory respect for the polarity of the connection.

5. If the test fails, replace the relay.