Checking the relay (Renault Scenic 1)

Many electrical circuits have a relay in their structure. A switching relay works like a switch. For example, in order to turn on the high beam headlights using a manual switch, you need to manually press it or move it to the desired position. In this case, the relay "receives an order" to supply power to the corresponding consumer. Of course, the voltage from the battery to the consumer could be supplied directly through the switch. But in the electrical circuit of all devices consuming high current (headlights, windshield wipers, fog lights), a relay is included as an intermediate link in order not to overload the switch or to shorten the current path. Along with such switching relays, there are control relays, for example, for the windshield wiper and washer or a time relay for interior lighting.

Checking switching relays

When the corresponding consumer is switched on, the voltage supplied to the relay closes its electric circuit and the current flows from terminal 2 to terminal 1. The magnetic coil inside the relay attracts the contact, thus closing the circuit of the "working" current. The "working" current flows from the relay to the consumer.

The easiest way to check the relay's functionality is to replace it with a known good relay. This is what workshops do. But since a car enthusiast does not always have spare relays at 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.

Please note! The terminal designations specified in the text may differ from the designations for serial relays installed on the corresponding vehicle.

3. First check with a voltage tester whether voltage is supplied to the (+) terminal on the relay holder. To do this, connect the tester to the "ground" (-), 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, use the circuit diagram to find an open circuit from the positive pole of the battery to the (+) terminal of the relay holder.

4. Make a jumper from a piece of insulated wire, stripping its ends.

5. Connect this jumper to the (+) terminal on the relay holder (voltage is supplied here constantly from the battery) with a relay closing contact. 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 we can assume that the relay is faulty.

If the consumer does not work in this case either, find out if the consumer connection to the "ground" (-) of the car is working properly. Then, using the circuit diagram, find and eliminate the break in the circuit from terminal 87 of the relay to the current consumer.

6. Install a new relay if necessary.

Caution! The relay plug connections located in the engine compartment are subject to corrosion just like other connections. For this reason, find out whether the relay failure is caused by water ingress.

In such cases, it is recommended to do the following:

7. Lubricate the plug connections on the relay with a special grease, for example, MOLYKOTE 33 Medium.

8. Remove the plug, clean its contacts with a metal brush, and then lubricate them with a special lubricant.

Install the relay, cover it with a lid and seal the lid with suitable water-resistant adhesive tape.

10. Check the relay fit and the condition of the wiring harness. The harness should "go" strictly vertically downwards.