Relay test

Relays are built into many current loops. The switching relay works like a switch. For example: When the high beam is turned on via the manual switch, the relay is commanded to energize the high beam lamps. You can, of course, supply current from the battery to the lamps directly through the manual switch. All consumers of electricity with high current (driving lights, windshield wipers, fog lights) relays are switched on so as not to overload the circuit breaker and provide the shortest path for the current. In addition to these switching relays, there are also functional relays, for example for the windshield washer/wiper system or relay for the ambient light switch-on signal.

Checking switching relays

When the corresponding consumer is turned on, a control signal is applied to the relay, which means that the magnetic coil inside the relay pulls the contact and closes the circuit "operating current". The operating current flows through the relay further to the consumer.

The easiest way to check the health of the relay is to replace it with a known good one. This is how they do it in workshops. Since amateurs very rarely have a working spare relay at their disposal, the next step is recommended with the so-called switching relay, which, among other things, is used to turn on the fog and main lights.

1. Remove the relay from the holder.

2. Turn on the ignition and the appropriate switch.

3. First, use a voltage indicator to determine if voltage is applied to the corresponding positive terminal of the relay socket. To do this, connect the indicator to ground and carefully insert the other contact into the terminal. If the indicator LED lights up, voltage is being applied. If the indicator showed no voltage, check the wiring for an open from the positive pole of the battery to the terminal according to the diagram.


4. Make a jumper from a piece of insulated wire, the ends must be stripped.

5. Connect this jumper in the relay socket to the positive terminal of the battery, which constantly conducts voltage with the relay output. This is almost the same as inserting a working relay. The location of the terminals in the relay socket can be identified by the colors of the cables according to the diagram.

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

7. If the main beam does not light up, determine if the headlight ground connection is good. Then check for an open in the wire from the relay terminal to the headlight based on the diagram.

8. If required, insert a new relay.