In a car factory or workshop with a good level of connection and wiring, of course, are not made on twists, but by crimping through bushings / sleeves / brackets or by ultrasonic welding. The ultrasonic device for welding wires is a professional device and it is not found in the arsenal of a garage foreman. But crimping with sleeves or brackets is a simple procedure, the tools (crimping pliers, crimper) and consumables are inexpensive, and you can connect wires with this method as well as at the factory.
However, many have the skills of soldering and skillfully own a soldering iron, solder and rosin. Solder the connection instead of crimping it with a sleeve – why not, if the soldering iron is at hand, but the crimper is not? However, there is often an opinion that soldering in the car electrical wiring is unacceptable. What is the reason? Let us explain!
When preparing for soldering, copper wires are neglected – they are covered with a layer of flux solder (which is still the best quality even in the XXI century old-good rosin), which gives fluidity to the solder and insulates the point of soldering with oxygen from oxidation. However, earned copper wire at the junction of the solder-soaked bare part and impregnated, hidden under the insulation, loses elasticity and acquires a certain fragility. In the dry language of science – in the process of heating the wire made by the method of cold deformation (which is a method that produces almost all the wire used for electrical wiring), recrystallization processes occur that lead to a change in the physical and mechanical properties of copper, reducing resistance to bending.
The buried and then soldered conductors at the points marked by arrows become more brittle than the original wire. In order to break a stranded copper wire with your hands, you need to bend it up to a hundred times in a row, and brazed enough to bend at the above points to break twenty times and it will fall off.
Do you agree that it sounds convincing not to use soldering to connect wires in the machine? However, not everything is so terrible, and those who have an understanding of the processes and skills of soldering, use it in car wiring easily, without problems and almost without any restrictions!
Yes, the car in motion experiences endless vibrations, often very intense. And if the soldered wire is free to hang under the hood on the length of half a meter, like a rope bridge over a river, after some time wiggling and chattering it can really give a fracture at the border of soldering and insulation. But even under such low real conditions, it will not happen soon, and it is not a fact that it will happen at all.
In fact, the car does not have any hanging conductors in the electrical equipment. The wires are bundled, tied up, laid along the body elements and fastened. The sagging and unsupported areas of the type of outputs to the sensors or headlamps are usually very short. If repair is carried out, and the wires are lengthened, joined or thrown new, replacing and duplicating staff (in which the contact is lost and it is more difficult to find it than to throw a “double”), then all these new wires are also either reeled with tape or plastic ties to the native bundles, or are placed in the protective electrical wiring corrugations, clasped. Therefore, significant vibrations of the wires, which can destroy the soldered joint by vibration, are practically eliminated! And it is possible to connect wires by soldering!
There are two basic conditions for a reliable soldering connection. The first is the generous use of heat shrink, which provides, in addition to the electrical insulation of the connection is no less important mechanical protection against steep bending and the risk of the same fracture on the border of the earned and undeserved part. Heat shrink tube should not only close the place of junction, but also have a couple of centimeters of allowance on either side of it. And for rigid conductors of large cross-section solder is appropriate to tighten the double or even triple layer of shrinkage one on top of the other.
Note another thing: the use of expensive and not always available special heat shrink with an adhesive layer inside to protect the solder from moisture, which is often recommended by the same car bloggers, is not necessarily even for under-hood connections. Yes, for twisting, such protection is very useful, because the penetrating moisture oxidizes the conductors at the points where they are pressed against each other. Soldering moisture is not afraid in principle, and parts of the wire outside of the soldering, going into the insulation, soaked with rosin during maintenance and do not let moisture under the insulation, inside the wire. Therefore, to protect the soldering is enough the most usual cheap shrinkage – just to best fit the diameter.
In the same way, the soldering is used to perform branching of wires, joints, soldering connectors, etc.:
And the second, even more important condition is the careful fixing of conductors that use soldering, clamps or tape to standard bundles or other fixed elements under the hood, torpedo, etc. The red wire in the photo is just in the middle of a heat-shrinkable soldering, the place of which is tackled by ties to a thick and rigid bundle above and below the connection and is thus fully protected from vibrations that can lead to buckling:
Are the fears about the inadmissibility of soldering electrical wiring not based on anything at all? It is very likely that rumors about the extreme fragility of brazed wires have arisen from the use of so-called “brazed acid” as a flux, which is usually zinc chloride (zinc dissolved in hydrochloric acid).
Acid is used for soldering of various coarse chemetes, for electrical compounds it is not accepted. However, it is often used by Chinese small producers of all kinds of household electronic shit with a predominance in the production process of manual installation. “Soldering wires serve the ends of wires before soldering for maximum process speed not by soldering iron and rosin, but by alternating dip in a cup with zinc chloride solution and a cup with molten solder.
At first, this may not cause any problems, but over time, the wire at the junction of the cured and bare copper part begins to break down with acid residue, the cores become green, thin and break even from a slight bend. But, frankly speaking, in the soldering of car wires such a situation can only take place with a catastrophic ignorance of the soldering operator, and indiscriminately spread the “acid problem” on soldering in general – the same as to scold a gasoline car for not going on a tank-filled diesel …