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Automotive Wire Basics
By Wayne Scraba /
Printable version
Degree of DifficultyEasy
Estimated Time240 minutes
240 minutes
Silver-, Tin, and Teflon-Plated Multi-Strand
Since most automotive wire is not protected from the environment or from contamination, it usually has a service life of about 10 years. After that, the deterioration process begins. Can this wear-and-tear be thwarted? Yes, but the wire must be plated prior to the stranding process. That’s where the silver-plated copper wire comes in, but more common plating is by way of tin. It is relatively easy to process and once applied, makes the copper wire much more resistant to chemicals and good old-fashioned air and moisture contamination than non-plated copper. FYI, wire that’s sold for aviation applications is usually tin-plated.
As automotive and aviation wire evolved, the covering material went from shellacked cotton braid to plastic to PVC plastic to compounds fortified with synthetic braids. PVC-covered wire is pretty common today, but plastic isn’t perfect. In fact, it’s porous. Contaminants eventually pass through a PVC jacket and attack the wire (particularly unplated copper wire). Another solution is a wire jacket manufactured from Teflon. From a wire covering perspective, Teflon is miraculous stuff. It remains flexible and soft at both ends of its operating temperature. Unfortunately, Teflon isn’t perfect either. The material isn’t very resistant to abrasion. Within the aircraft industry, the solution was to wrap the Teflon coated wire with a PVC jacket. That’s a major cost factor since the wire must first be plated in silver or nickel, before the Teflon can be formed over the bundle. Then there’s one more issue with Teflon-wrapped wire: In a fire, Teflon can give off fumes that are toxic to breathers.
PVC-Insulated Wire
That definitely narrows the choices for wire you can use to wire those driving lamps or the winch in your vehicle. PVC insulated wire can be used in most locations, with the possible exception of a spot very close to the engine. There are two temperature ranges found in most PVC insulation that is readily available: One is rated at 221 degrees Fahrenheit, while the other is rated at 176 degrees Fahrenheit. A Teflon jacket is different. It won’t melt at temperatures in the 400-500-degree Fahrenheit range. What sort of temperatures do cars reach? Wiring outside of the engine compartment can often encounter temperatures as high as 180 degrees, but engine compartment temperatures can go as high as 300 degrees or more in specific locations. Mix in the chemicals used in automobiles, and you can see we’re asking a lot from wire jackets.
You might hear the word “Tefzel” when it comes to wire jackets or sleeves. This stuff is related to Teflon, but it isn’t quite as resistant to high temperatures. It’s more abrasion-resistant though. For certain applications, it might be perfect, but you won’t be able to find it at the local auto parts store. It can be located at aircraft avionics shops and at some aircraft surplus outlets. For the most part, Tefzel is manufactured in a good range of gauge sizes but it’s not cheap. If high temperature and abrasion protection are critical, you’ll find there are some different wire sleeves that can be added to the wire harness. Several aftermarket ignition component manufacturers offer varied products for the purpose.
When all is said and done, there really is one path to follow when picking wire for your automotive electrical jobs. Use fine, multi-strand copper wire. The more strands in the core, the better. If you can afford it, use a silver-plated or nickel-plated wire, and if you can’t swing the cost, use a tin-plated copper wire. If the wire has a PVC jacket, keep an eye out for excessive heat. If you select Teflon-jacketed wire, watch for potential abrasion. Consider using an extra wire over-wrap, and don’t forget to support an added harness (don’t let it dangle in the breeze). In the end, better quality wire will definitely last longer and cause far fewer maintenance headaches. We can all relate to that.
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