Discussion on wet zone sealing of automobile wiring harness

The Automotive connector Single Wire Seal connects the electrical parts of the whole vehicle together, which is the neural network of the automobile, and guarantees the normal operation of the electrical functional parts of the automobile. With the increasing level of modern automobile electronization, the durability and reliability of wire harness are required to be higher, especially for the wire harness in the engine room and the harsh environment under the vehicle body.

A wet area

We put the car engine room and under the car body part exposed to the air can be frequently affected by rain, water area called wet area; Relatively, the cab, luggage compartment is basically not affected by rain, water part of the dry area.

Seal wet area

The electrical components and wiring harnesses in the ten zones are less affected by the environment of high temperature, high humidity, chemicals, dust, etc. However, electrical parts and wiring harnesses in wet areas are greatly affected by the environment, so they must be well protected against high temperature, water and corrosion. If the sealing of the electrical parts in the wet area is not good, it will lead to water inside the electrical parts, which will cause the electrical parts’ internal short-circuit, rust, ablative and other faults and lead to abnormal electrical functions or failure. Similarly, poor sealing of wiring harness interconnections and plug-in connections can also cause flooding and electrical failure. Therefore, we define the wet zone sealing as the sealing treatment of the electrical function parts and wiring harness connection parts in the wet zone of the automobile to isolate the water and ensure the normal and reliable protective operation of electrical functions.

There are two main ways to enter water into electrical system: one is to rely on the gravity of water to infiltrate into electrical module or indirectly infiltrate into electrical module through Automotive connector Seal, wiring harness point, wiring harness iron point; Second, due to siphoning, water molecules enter the electrical module through the gap between multiple copper wires.

Siphon phenomenon refers to the phenomenon that liquid flows through the curved pipe to the higher liquid level and flows downward to the lower liquid level under the action of intermolecular gravity and atmospheric pressure, as shown in figure 1. In the automobile, when the electrical module is working, the internal temperature rises, and when the stop working temperature decreases, the internal pressure decreases. At this time, under the action of the pressure difference, water molecules penetrate into the electrical module through the gap of the poorly sealed multi-wire, causing electrical fault.

Talk about the use of sealing ring on automobile wiring harness.

The durability and reliability of automobile parts have been paid more and more attention. As a protective material, rubber parts are widely used in automobiles. Among them, the importance of sealing ring is self-evident, especially for the wiring harness protection of engine nacelles and underchassis of automobiles. There is a “wet zone” here. In general, we call the “wet zone” where the engine compartment and the underbody of the car are exposed to the air and often affected by rain and water, and the “dry zone” where the cockpit and trunk are largely unaffected by rain.

One of the most important functions of Automotive connector Single Wire Seal is to separate wet and dry areas. This is an application. In addition, sealing rings should be installed at the ABS harness of left and right rear wheels. Specifically, under the rear seats (such as golf), there is a sealing ring to separate the inside and outside parts, so as to ensure that the water at the bottom will not leak into the cab during driving.

Every qualified wire harness will be tested by gas seal to ensure that the sealing ring on the wire harness can work. Generally, in the wire harness factory, we use vacuum test and detection equipment to carry out the work.

The working principle of the equipment is very simple, put the sealing ring on the mold, the equipment provides a continuously increasing pressure value, the air inside out, in a certain time and pressure value, if the sealing ring can withstand, it is a good product, otherwise there will be quality problems.

In addition, electronic appliances and harness of the dry zone affected by the high temperature/humidity and chemical/dust is small, wet area is just on the contrary, if the seal bad, may lead to electrical appliances and wiring harness water, internal short circuit/corrosion caused by directly lead to function failure, which requires the wiring harness connector plug a complete sealing protection, for example, audi A3 in the project of the nacelle ESP – SG plug there are air tightness design, open the connector, you can see one layer of sealing ring (with oil), sealed performance is good or bad is directly related to its function is normal.

There are two main ways for electronic components such as connectors to enter water. The first is that external liquid penetrates into its interior by gravity, such as connectors without sealing ring, or water enters from internal connection points of wire harness (such as unprotected solder/pressure contact/lapping point). Emphasized the word “siphon” here, because it is a certain temperature when general electric in the work, the internal air to form a certain pressure, when to stop working, the temperature drop, the internal pressure is small, can form pressure difference at this moment, if the connector is sealed, the water vapor will be down much of the gap between copper wire inside, and lead to function failure; Therefore, the wet area connector will generally require a sealing ring (pad).

For connector sealing test, the general Wiring Harness Single Wire Seal manufacturer is  integrated in the electronic test bench, the corresponding connector test module will bring sealing test, is to give it a rated pressure value, while testing its conductivity and sealing performance.

Summary, the sealing ring is the important parts of the wiring harness, its quality is directly related to the function of the wiring harness, either directly using in on the wiring harness connector, I have met the problem, the former see problem is surface holes or more, direct reason is the material to cut corners or mishandling the rubber in the vulcanization process; Connector is common internal seal ring assembly is not in place, the whole is not on a plane leading to air leakage; To find out the root cause of the problem as soon as possible and take precautions is what we wiring harness practitioners should consider.