For example, in order to turn on a consumer using a manual switch, you must manually press it or move it to the desired position. Relay in this case «receives an order» supply power to the appropriate consumer.
Of course, the voltage from the battery to the consumer could also be applied directly through the switch. But in the electrical circuit of all devices that consume high current (headlights, windshield wipers, fog lights), as an intermediate link, they include a relay so as not to overload the switch, or to shorten the current path.
Checking switching relays
When the corresponding consumer is turned on, the voltage supplied to the relay closes its electrical circuit.
The magnetic coil inside the relay attracts the contact, thus completing the circuit «working» current. «Worker» current flows from the relay to the consumer.
The easiest way to test a relay is to replace it with a known-good relay. That's how they do it in workshops. But since the motorist does not always have spare relays on hand, the following approach is recommended when checking them.
1. Remove the relay from the holder.
2. Turn on the ignition and the appropriate switch.
3. Check first with a voltage tester whether voltage is applied to the terminal (+) on the relay holder. To do this, connect the tester to «mass» (-), and carefully place the other contact rod on the terminal (+).
If the tester's LED lights up, then there is voltage. If the tester does not register voltage, look at the circuit diagram for an open circuit from the positive pole of the battery to the terminal (+) relay holder.
4. Make a jumper from a piece of insulated wire, exposing its ends.
5. Connect this jumper to the terminal (+) on the relay holder (voltage is applied here constantly) with relay closing contact. This technique does almost the same thing that a good relay should do. The location of the terminals on the relay holder can be determined by the color of the insulation of the connected wires or by the wiring diagram.
If, for example, the main beam lights up when the jumper is connected, then it can be assumed that the relay is defective.
If the high beam does not come on, find out if the connection between the headlight and the body is good «weight» (-) car. Then, according to the circuit diagram, find and repair an open in the circuit from the relay terminal to the main headlight.
6. Install a new relay if necessary.
Attention! If the relay functions intermittently, then the problem, as a rule, should be sought in the relay itself. Sometimes there is a so-called gluing of the relay contact, as a result of which it does not open, although the relay otherwise works flawlessly. If this problem is detected, you just need to knock on the relay housing. If this relay closes again, replace this relay with a new one.