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 corresponding switch.
3. First check with a voltage tester whether voltage is applied to terminal 30 (+) on the relay holder. To do this, connect the tester to «mass» (-), and carefully place the other contact rod on terminal 30 (+). 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 terminal 30 (+) relay holder.
4. Make a jumper from a piece of insulated wire, stripping its ends from insulation.
5. Connect this jumper to terminal 30 (+) on the relay holder (voltage is supplied here constantly from the battery) with a normally open relay contact 87. This technique does almost the same thing that a working relay should do. The location of the terminals on the relay holder can be determined by the markings on the contacts or on the relay itself.
If the corresponding network consumer works with the jumper connected, then it can be assumed that the relay is faulty.
If the consumer does not work in this case, find out if the connection of the consumer is working properly on «mass» (-) car. Then, according to the circuit diagram, find and repair an open in the circuit from terminal 87 of the relay to the current consumer.
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 rest of the relay 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.
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