Auto Relays

Auto recloser relay control higher voltages or currents by using lower voltages or currents. When a certain voltage or current is applied to both ends of the electromagnetic relay coil, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, the yoke, the armature and the working air gap of the magnetic circuit. Under the action of the magnetic field, the armature is attracted to the pole face of the iron core. Therefore, the normally closed contact of the contact is pushed to be disconnected, and the normally open contact is closed. When the voltage or current at both ends of the coil is less than a certain value, and the mechanical reaction force is greater than the electromagnetic attraction force, the armature will return to the initial state, the normally open contact is disconnected and normally closed contact is on.

How To Test Auto Relays？

(1) A simple method for judging the working performance of the relay.

Turn on the ignition switch, and then use your ear or stethoscope to listen to the sound of the control relay, or feel the vibration of the relay with your hand. If there is vibration, then the relay is working well, the electrical appliance does not work due to other reasons. Otherwise, the relay is not working properly.

You can also unplug the relay for testing, for example, if the air conditioner compressor does not work, you can start the engine, turn on the blower switch and the air conditioner switch. Then unplug the connector of the air conditioner compressor relay to judge. If the sound of the relay action can be heard, the engine speed drops significantly when the relay is unplugged, and the engine speed rises when the relay is inserted, it means that the air conditioner compressor relay and its control circuit are normal.

(2) Common failures of relays.

Common failure phenomena of relays include coil burnout, inter-turn short circuit or insulation aging, contact ablation, thermal decay, and inability to adjust the initial operating current.

①The relay coil is burnt out. In order to prevent this from happening, if the temperature may exceed 80°C during repair, maintenance and electric welding, the temperature-sensitive relays and electronic control units should be removed.

② Contact ablation. For example, vehicle with 491Q-ME engine, the relay of the air conditioner condenser fan is just below the glass cleaning spray pipe. If the spray pipe is broken, the cleaning fluid will leak to the relay, making the relay normally open contact is corroded and cannot be disconnected, which will lead to the failure of the air conditioner condenser fan to keep running. Therefore, water should be strictly prevented from entering the relay.

(3) Try to reduce the contact resistance of the relay contact

The contact resistance existing between the contacts of the automotive relay is mainly composed of shrinkage resistance and surface film resistance. The contact resistance of the contact is related to the contact form, material properties and surface processing of the contact. It can be seen that to reduce the contact resistance of the relay contacts, under the condition of a certain contact pressure, it can be started by improving the contact state and improving the contact material.

(4) Poor grounding of the ECU may affect the normal operation of the relay

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