Checking the relay (Mazda 121 (3))

Many circuits have relays that act as switches. Example: when the high beam is turned on manually, the relay receives a signal and supplies voltage to the lamp. Of course, you can supply current from the battery to the lamp directly through the light switch. However, all consumers with high current consumption (high beam, windscreen wipers, fog lights) relays are included in the power supply circuit to avoid overloading the switches and to provide a short path for the voltage. In addition to switching relays, there are also functional relays, such as a windshield wiper/washer relay or a signal relay for external lighting being on.

Checking switching devices

When the corresponding consumer is switched on, the relay is activated, i.e., under the influence of the control current, the electromagnet inside the relay closes the working contacts, through which the main current passes to the consumer.

The easiest way to check the functionality of a relay is to replace it with a known good one. This is usually done in a workshop. Since a car often lacks this capability, the following check procedure is recommended for switching relays. The relay contact designations given below are standard, but may sometimes differ.

Pull the relay out of its socket.

Turn on the ignition and the corresponding switch.

First, check with a voltmeter whether voltage is supplied to contact 30(+) in the relay socket. To do this, connect the voltmeter wires to the "ground" and to the specified contact. If there is no voltage, then check the voltage supply circuit from the positive contact of the storage battery to contact 30 in the relay socket in accordance with the electrical equipment diagrams.



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

Using the jumper you made, close contact 30 in the relay socket (it is supplied with voltage from the battery) and the output contact from the relay (usually denoted as 87). In this way, the operation of a working relay is simulated. The contact number designations are usually located on the relay or on its socket.

If the consumer starts working when the contacts are closed with a jumper (for example, the headlights came on), then this means that the relay is faulty.

Content based on information from [MazBook.ru]

If the consumer does not work, then you need to find out whether it is well connected to the "ground". Then you need to check the voltage supply circuit from contact 87 in the socket to the consumer.

Replace the relay if necessary.

Note: If the fault in the voltage supply circuit appears occasionally, then this is usually due to a fault in the relay, i.e. its contacts close normally at a time when the relay is working normally. If the relay fails to work, you need to knock on its body. If the relay works normally, then it needs to be replaced.