Relay test

Relays are built into many electrical circuits. The switching relay works as a switch. When the high beam is turned on by the manual switch, the relay is commanded to energize the high beam headlights. Of course, it would be possible to supply current to the high beam headlights from the battery directly through the light switch. However, for all consumers requiring high current, an intermediate relay is included so as not to overload the switch and guarantee the target from a short circuit. In addition to switching, there are also, for example, intermittent wiper relays.

Checking the switching relay

The relay is activated when the corresponding consumer is turned on. In this case, due to the switching current, the electromagnet coil inside the relay attracts the contact and thereby closes the electrical circuit of the operating current. The operating current flows further to the consumer.

The easiest way to check the performance of the relay is to replace it with a good one. This is how they do it in the workshop. Since the motorist only in very rare cases has a new relay at his disposal, the following sequence of operations with the so-called switching relays is recommended. The terminal designations given below, especially for serially installed relays, may differ.

Pull the relay out of the board.

Turn on the ignition and the corresponding switch.

First, using a voltage tester, check whether voltage is applied to terminal 30 (+) relay boards. To do this, connect one electrode of the tester to ground (-), and carefully insert the other electrode with a sharp end into terminal 30. If the light diode of the device lights up, then voltage is applied. If the device shows no voltage, guided by the electrical circuit, find an open circuit in the area from the positive pole (+) battery to terminal 30.


Make a jumper from a piece of insulated wire, polishing the ends of the jumper to shine.

Connect this jumper to terminal 30 of the relay board (this terminal is always supplied with voltage from the positive pole of the battery) with terminal 87 on the relay output. This operation practically does the same thing that a good relay does. Where the relay board terminals are located is indicated on the relay or on its pin contacts.

If the current consumer works with the jumper installed, it can be concluded that the relay is faulty.

If the current consumer does not work, it is necessary to find out if its connection to ground is working properly. Then, guided by the electrical diagram, find and repair an open in the wiring from terminal 87 to the consumer.

If required, install a new relay.

Attention: If a malfunction in the electrical circuit with a relay occurs only from time to time, then the cause is usually due to a defect in this relay. In this case, the relay contact remains closed or open, while the rest of the time the relay functions flawlessly. If this kind of malfunction occurs, it is easy to knock on the relay housing. If the relay trips as a result, it should be replaced.