Relay — description and testing (VW Transporter T4)

Relays are found in many current circuits. Switching relays work as a switch. For example: if the high beam is turned on manually by the switch, then the corresponding relay receives a signal to supply current to the high beam lamps. Many current-intensive consumers (headlights, wipers, fog lights) the circuit contains relays in order not to overload the switch or to have a shorter current path. There are also functional relays, such as glass cleaning and washing systems or interior lighting time relays.

Examination

The relay's connecting contacts are standardized. When the consumer is switched on, the relay is controlled. This means that by supplying the switching current to terminal 68, the switching circuit to terminal 85 is closed. The magnetic coil inside the relay pulls in the core and closes the current circuit "Working current". "Working current" goes from terminal 30 through the relay and terminal 87 further to the consumer.

The easiest way to check the relay's functionality is to replace it with a new, working one. This is also done at service stations. Since an amateur does not always have the necessary relay at hand, the following working techniques are recommended for handling the switching relay, which, among other things, are used to switch on headlights and fog lights. The terminal designations given here may differ, first of all, from serially installed relays.

1. Pull the relay out of the socket.

2. Turn on the ignition and the corresponding switch.

3. First, check the presence of voltage at terminal 30 (+) in the relay socket using a voltage indicator. To do this, connect the indicator to ground (-), carefully attach the second wire to terminal 30 in the relay socket. If the indicator diode lights up, there is voltage. If the indicator does not show voltage, determine the break in the circuit from the positive pole of the battery (+) to terminal 30 using the electrical diagram.



4. Make a jumper from insulated wire, stripping its ends.

5. Connect this jumper in the socket terminal 30 (+) of the battery, always under voltage) with the output of the relay switch terminal 87. This method does the same thing that a working relay would do if it were installed.

6. If, for example, the high beam lights up when the jumper is installed, then the relay is faulty.

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7. If the high beam does not light, find out if there is a ground connection to the headlight. Then, using the electrical circuit, find the break in the wire from terminal 87 to the headlight and fix it.

8. Replace the relay if necessary.