(1) easy to judge the working performance of the relay
Turn the ignition switch, and then use the ear or stethoscope to listen to the control relay with or without sound, or feel the relay has no sense of vibration, if any, indicating that the basic work of the relay, the electrical does not work is caused by other reasons ; Otherwise, indicating that the relay is working abnormally.
It is also possible to unplug the relay for testing, for example if a malfunction of the air conditioning compressor does not work, the engine can be started and the blower switch and air conditioner switch turned on. Then unplug the air conditioner compressor relay connector to judge. If you can hear the sound of the relay, and unplug the relay when the engine speed dropped significantly, insert the relay when the engine speed and increase, indicating the air conditioner compressor relay and its control circuit is normal.
Relays on the location, usually in the circuit diagram marked with a dotted line of the relay and fuse, generally arranged in the central distribution box.
(2) common fault relay relay Common fault phenomena are: coil blowing, turn short circuit (insulation aging), contact ablation, thermal decay, and can not adjust the initial action current.
① relay coil burn out. To prevent this from happening, remove the temperature-sensitive relays and ECUs during maintenance, care and welding if the temperature may exceed 80 ° C.
② contact ablation. For example, the Gold Cup Sea Lion sedan (with 491Q-ME engine) air conditioner condenser fan relay, it is located in the glass cleaning sprinkler below, if the spout rupture, the cleaning fluid will leak to the relay, the relay normally open Contact corrosion and can not be disconnected, will lead to air-conditioning condenser fan constantly stop failure. Therefore, should prevent the relay water.
(3) Try to reduce the contact resistance of the relay contacts
Contact resistance exists between the contacts of the vehicle relay, mainly by the shrinking resistance and surface film resistance of two parts. Contact resistance and contact contact form, material properties and surface processing and other factors. Thus, to reduce the contact resistance of relay contacts, contact pressure in the case of a certain, you can improve the contact state and improve the contact material to start.
(4) ECU overdriving may affect the normal operation of the relay A Shenlong Beverly 988 sedan, in normal driving, the engine automatically stalls, start again, unable to drive. Turn the ignition switch, can not hear the sound of the fuel pump operation, there is no high-pressure fire. Check the ignition coil and found no power plug, but the primary and secondary resistance are normal. Measuring the car's jet double sealed relays, the plug has a 12V power supply. Replace jet double sealed relays, or no high-pressure fire, there is no relay pull the sound. A wire will be sprayed double sealed relay No. 10 feet directly to the ground, can hear the sound of the relay pull, the engine also started successfully. But the strange thing is, open the ground line, the engine does not turn off, and turn off the ignition switch, restart the engine, normal. Analysis of the reasons, which is due to poor grounding of the engine ECU, resulting in the relay coil supply voltage is very low (sometimes only 2V or so), it is impossible to make the relay pull. With the lead directly to the ground, the relay has a 12V voltage, so smooth pull, so the engine starts successfully. After removing the temporary grounding wire (the ignition switch is still on), the relay still has a lower holding voltage (this is the common characteristic of the relay). Even if the holding voltage is only 2V, the relay will not break Open, so the engine does not turn off. Turn off the ignition switch, the circuit produces self-inductance electromotive force is much higher than the supply voltage, in this strong electromotive force, poor access to the ground may be back to normal, so the engine starts normally. However, these failures will be reproduced, so the eradication approach is to take the wrong parts of the ground thoroughly.
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