Example: When the manual switch is turned on, the relay is instructed to apply voltage to the high beam headlights. Of course, it would be possible to supply voltage from the battery to the high beam headlights directly through the switch. However, for all powerful consumers, an intermediate relay is switched on so as not to overload the circuit breaker or to provide a shorter voltage transmission path. In addition to the switching relay, there are also functional relays, for example for the windshield wiper system or the warning horn relay when the outside lights are on.
Checking the enable relay
When the corresponding consumer is switched on, the relay is activated, that is, under the influence of the switching current, the electromagnetic coil inside the relay attracts the contact and thus supplies "operating current" to the current circuit. The operating current flows through the relay to the consumer.
The easiest way to check the functioning of the relay is to replace it with a known good one. This is also done at the service station, but at home there is not always an extra relay, so the following method is recommended for the so-called switching relays, as they are often called in relation to turning on the main and fog lights.
Remove the relay from the block.
Turn on the ignition and the corresponding switch.
First, test the presence of voltage at the corresponding terminal with a probe (+). To do this, connect one wire of the probe to ground, and carefully insert the other into the terminal. If the probe lamp lights up, there is voltage. If there is no voltage, find an open in the electrical circuit between the battery and the terminal.
Make a jumper from an insulated wire, strip the ends.
Connect a jumper on the relay block terminal (+) battery, always energized, with a relay output contact. This achieves the effect, as if a replacement was carried out with a known-good relay. The location of the terminals on the relay block is determined by the color of the wires or by the electrical diagram.
If with a jumper the high beam headlights, for example, light up, the relay is faulty.
If the high beam does not work, find out if the headlight ground connection is OK. Then, using the electrical circuit, find and repair the wire break.
If required, install a new relay.