Relays are electromagnetic switches that use small currents in the coil to control significantly higher operating currents. Standard relays have four or five connectors. The markings are numerical and are 30 (permanent plus), 86 (plus on the coil), 85 minus (output from the coil), and 87 minus (output to the consumer). If there is a fifth connector, it is labeled 87a.
Relay and circuit
Due to the heavy use of relays on the vehicle, we will explain the standard test procedure. The relays are located on the relay plate with the other relays and fuses. Testing the relay is done in two stages: checking the correctness of the relay base on the plate and testing the relay on the workbench. Before testing, it is necessary to get to know the electrical connection diagram and the position of the components.
Relay wiring diagram for lights
First, the correctness of the system is checked, in our case, the operation of the main beam on the vehicle. If turning on the main beam headlights switch does not turn on both lights, the electrical diagram shows that the relay is one of the possible malfunctions.
From the information system, we get to know the position of the lighting relay on the vehicle. We remove the relay from the plate and perform a visual inspection of the exterior of the housing and connectors. If the relay is visibly damaged, replace it with a new one.
We determine the arrangement of connections (numbers) on the relay socket.
First, we check the voltage between terminals 85 and 86. We connect the voltmeter and turn on the main beam switch. If the measured voltage is 0 V, there is a fault in the power supply of the relay coil. It is necessary to carry out additional tests and determine the location of the failure. If the measured nominal voltage is 12 V, the power supply to the relay coil is correct.
Then there is a check of the main beam power supply via the relay. Short-circuit terminals 30 and 87 are on the relay socket. We turn on the main beam through. If the main beam bulbs do not light up, there is a fault in the power supply of the bulbs. It is necessary to carry out additional tests and locate the fault. If the main beam bulbs light up, the relay socket is correct, and we move on to testing the relay itself.
Relay testing is done with an ohmmeter.
First, measure the resistance of the relay coil between connectors 85 and 86. The expected resistance value is 70-120 Ω. For the exact value of the tested relay, use the information system. If the measured value is not within the specified limits, the relay winding is defective, and it is necessary to replace the relay with a new one. If the measured value is within the specified limits, the relay winding is correct.
After winding, check the entire relay. A 12 V power supply is supplied to the coils of relays 85 and 86. We connect an ohmmeter to connectors 30 and 87. If the resistance is infinite after switching on the relay, the relay is faulty and needs to be replaced. If the resistance is 0 Ω, the relay is working.
In new vehicles, it is not allowed to use a test lamp with a light bulb due to the possible transfer of high current and damage to the ECU. Take care of the pinout when testing.
To perform a relay test, follow these steps:
System overview
Check the correctness of the system. Get to know the wiring diagram of the system. Determine the location of the relay on the vehicle. We remove the relay from the plate and perform a visual check of the state of the relay. If the relay is visibly damaged, replace it with a new one.
Testing of the relay socket
Determine the layout of the pins on the relay socket. Turn on the system. Measure the voltage between connectors 85 and 86. If the voltage is 0 V, perform additional tests and determine the fault. If the voltage is 12 V, short-circuit connectors 30 and 87. If the consumer does not turn it on, perform additional tests and determine the fault. If the consumer turns on, the relay socket is good and continues testing the relay.
Testing the relay on the workbench
Measure the resistance of the relay coil between connectors 85 and 86. If the resistance is 0 V, replace the relay with a new one. If the measured resistance is 70-120 Ω, check the relay switch. Connect a 12 V supply to connectors 85 and 86 and measure the resistance between 30 and 87. If the resistance is 0 Ω, the relay is working. If the resistance is infinite, the relay is faulty and replaced with a new one. After replacing the relay, check the correctness of the system.
See also
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