I read an electronic magazine in which there is a report on the ways to check and repair the automotive relays, http://www.kynix.com/Parts/3873353/V23074A1001A403.html. After reading, I became interested in automotive relays. So I searched some related materials and information about this topic from google. Today I come to this forum to turn to you to discuss my understandings are appropriate.

Here are my personal understandings:

(1) relay work performance of the simple method of judging
Turn on the ignition switch, and then use the ears or stethoscope to listen to the control relay whether the suction sound, or feel the relay with a sense of vibration, if any, that relay work is normal, with electrical work is caused by other reasons ; Otherwise, that the relay work disorders.
You can also unplug the relay to test, for example, the occurrence of air conditioning compressor does not work failure, you can start the engine, and then turn on the blower switch and air conditioning switch. And then unplug the air conditioner compressor relay connector to judge. If you can hear the sound of the relay action, and pull the relay when the engine speed significantly decreased, insert the relay when the engine speed and upgrade, indicating that the air conditioning compressor relay and its control line is normal.
On the location of the relay, where the circuit schematic marked with a dotted line of the relay and the insurance, generally arranged in the central distribution box.
(2) Common faults of relays The common faults of the relay are: coil blown, interturn short circuit (insulation aging), contact ablation, thermal decay and can not adjust the initial operating current.
① relay coil burned. In order to prevent this from happening, the temperature-sensitive relays and electronic control units should be removed if the temperature may exceed 80 ° C during maintenance, maintenance and welding.
② contact ablation. For example, Jinbei sea lion car (using 491Q-ME engine) air conditioning condenser fan relay, it is just in the glass cleaning water pipe below, if the water pipe rupture, cleaning fluid will leak to the relay, so that the relay normally open Contact rust can not be broken, will lead to air conditioning condenser fan often turn the fault. Therefore, should prevent the relay water.
(3) try to reduce the contact resistance of the relay contacts
The contact resistance between the relay contacts is mainly composed of two parts: the shrinkage resistance and the surface film resistance. Contact contact resistance and contact with the contact form, material properties and surface processing and other factors. It can be seen, to reduce the relay contact contact resistance, contact pressure in a certain circumstances, you can improve the contact state and improve the contact material to start.
(4) ECU bad grounding may affect the normal work of a relay Shenlong Beverly 988 car, in normal driving, the engine automatically flameout, start again, can not be a car. Turn on the ignition switch, can not hear the sound of fuel pump operation, there is no high pressure fire. Detection of the ignition coil and found no power on the plug, but the primary and secondary side of the resistance are normal. Measure the car's dual-seal relay with a 12V power supply. Replace the jet double seal relay, or no high pressure fire, and no relay pull the sound. With a wire will be sprayed double sealed relay 10 feet directly to the ground, can hear the relay pull the sound, the engine also started successfully. But the strange thing is, open the root to take the wire, the engine does not turn off, and turn off the ignition switch, restart the engine, the normal. Analysis of the reasons, this is due to bad engine ECU ground, resulting in the relay coil supply voltage is very low (sometimes only about 2V), it is impossible to make the relay pull. With the wire directly after the ground, the relay has 12V voltage, so smooth pull, so the engine started successfully. (The switch is still in the state), the relay still has a low holding voltage (which is the common characteristics of the relay), this holding voltage even if only 2V, the relay will not break Open, so the engine does not turn off. Off the ignition switch, the circuit generated by the self-inductance electromotive force is much higher than the power supply voltage, in this powerful electromotive force under the action of poor contact with the ground may return to normal, so the engine started after the normal. But the fault will be reproduced, so the eradication of the way is to deal with bad parts of the ground completely.

Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of automotive relays. I need continual learnings.

What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.

May someone would like to help ?

thanks in advance