Checking switching relays
When the corresponding consumer is turned on, the voltage supplied to the relay closes its electrical circuit and the current flows from terminal 2 to terminal 1. The magnetic coil inside the relay attracts the contact, thus closing 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.
Attention! The terminal designations indicated in the text may differ from the designations for serial relays installed on the respective vehicle.
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 supplied here constantly from the battery) 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 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 defective.
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! Relay plug connections located in the engine compartment are subject to corrosion in the same way as other connections. For this reason, find out if the failure of the relay is caused by water ingress.
In such cases, it is recommended to do the following:
7. Lubricate the plug connections on the relay with special grease, eg MOLYKOTE 33 Medium.
8. Remove the plug, clean its contacts with a metal brush, and then lubricate with special grease.
Install the relay, cover it with a cover and insulate the cover with a suitable water-resistant adhesive tape.
10. Check the fit of the relay and the condition of the wiring harness. The tourniquet must «leave» strictly vertically down.