T&C general application failure mode and potential cause analysis of wiring harness system series (2)

2021-05-11 11:00 admin
2. Increased resistance
Common failure forms:
1. Increased voltage drop;
2. Loss of signal;
3. The loop is broken.
Speaking of this, some people may say that if you say less, it will cause ablation. Yes, the topic of ablation, I want to save it later, of course, if you're going to put it here, there is nothing wrong with it.
The problem of increased resistance is still a common phenomenon in vehicles. Speaking, it is a problem that is easy to troubleshoot, and the cause can usually be found. The harm should not be underestimated because it will cause shoddy work of electrical appliances, especially some switches, analog switches, by adjusting the resistance value of different gears to realize the controller to recognize the driver's intention. Now, usually, The current in the loop is minimal. If the terminal resistance in the connector is too large, it will cause the signal to be distorted, or it will not pass at all. Of course, those loops that send other signs will also have such potential problems.
Potential reasons:
1. Incorrect terminal selection (plating)
We all know that some terminal series may have different plating options, from tin to gold. Sometimes, tin-plated terminals are used on one end. What type of terminals are used for the other end of the airport that is mated with it? Is it better if you use gold-plated terminals?
The answer is obvious, and you must use the same type of plated terminals. The tin-gold combination is inferior to the tin-tin or gold-gold combination. Because after contact between different plating terminals, a galvanic effect will occur in a humid environment, which will speed up corrosion, increasing electrical resistance and reduced terminal life.
2. Terminals that have been reworked
The harm of reworked terminals has not been minor. As we have explained in the last lecture, it will cause many problems, including what we said today. The tool may be inserted into the female terminal by mistake during withdrawing from the airport. As a result, the contact gap of the female terminal becomes larger. After the male terminal is mated, the positive pressure of the female terminal contact to the male terminal becomes smaller or even disappears. Then the contact resistance becomes large, or even wholly unreasonable, which is expected.
3. Incorrect connector selection (use non-waterproof parts in wet areas)
When many people see this reason, they may laugh out loud-will those who engage in wiring harness fail to distinguish between wet and dry areas? Outdoors are wet areas, indoors are dry areas.
Of course, this seems obvious. But, in some places that seem to be indoors, we will still be positioned as wet areas, such as:
 Around the feet of the occupants (bring rain or snow into the room);
 Near the air conditioning pipeline (condensation water);
 On the door, outside of the waterproof membrane.
If you use the wrong connector, you will be exposed to more water vapor, and after a long time, the terminal will rust. So, next time you see that some electrical components are indoors but choose a sealed connector, it is best to think about it, don't be too subjective to believe that people are wrong, and use the seal for the female connector. Omit all in the name of saving unnecessary waste.
4. The connector is subjected to excessive vibration
(1) The actual vehicle vibration is greater than the standard
This problem has occurred in some domestic engines. At certain frequencies, the actual measured value is greater than the value in the specification, so it is reasonable for the connector to have a problem.
(2) The connector is used in the wrong place
The connector with a low vibration level is used in a place with a high vibration level. In this case, the time may not be too long, and the problem is exposed.
5. The terminal is stressed by the wire harness (the winding tape position is inappropriate)
The problem of the wrong tape winding position has been explained in detail in the previous lecture. After causing the pain of matching force, after the male and female connectors are mated, the male terminal in the female airport is inclined, which is not a natural state. This will lead to stress between the male and female terminals, which is a bit more vivid. In other words, the male airport is pinned inside the female terminal. When vibration is added (the beat is everywhere in the car), the wear between the male and female terminals will increase, and the coating will even be ground into powder and fall off the connector in a short time. It all happened. Then there is no need to say too much about the next thing-the resistance becomes larger, and the signal is lost. If it continues, it is likely to lose conduction.
---I would like to remind you again that too much tape at the end of the connector is not a small problem.
6. Wiring harness design problem (the terminal bears long wires and vibration, which causes deformation of the female terminal reed)
Also, it needs to be emphasized, don't use the trunk of the harness as the fixed point of the branch. This is a huge misunderstanding!