Automotive Electrical Systems - Positive Energy

"The biggest ammeter I've ever seen was 60 amps," Overholser observed. "Well, hardly anyone has a 60-amp alternator anymore; they're running 100-, 125-, 150-amp, or so. So if the battery is really low, guess what? All that power has to go through that ammeter to charge the battery. If it's a big alternator and the ammeter can't handle it, it can go up in flames."

"Some people say that amp gauges are totally out and that you'll burn your car down," Rich Fox noted. "If you're running the old amp gauges that are 10 or 15 amps, well yeah you got a problem. But if you have a 60-amp amp gauge and a normal alternator (one of equal or lesser value than the gauge) you probably won't burn your car down."

Still, he revealed another potential hazard: "You have to run that big wire up through the dash and back down to the ignition switch or fuse panel in order to run an ammeter."

"The only way you can safely use an ammeter is if you find a shunted ammeter," Overholser instructed. A shunted ammeter has a secondary resisted circuit in it that will prevent absolute meltdown in the event of overload.

Both Fox and Overholser agreed that a voltmeter is both safer and a more accurate gauge of the system's health. First, not all the power has to go through them. Second, "A voltmeter can use a 16-gauge wire because all it does is sense voltage," Fox said. What's more, a voltmeter lets you know in the simplest terms if the system has enough power. "It's the safe haven of telling you what's really going on," Fox concluded.

For example, a headlight switch may have enough capacity to handle normal sealed-beam headlights, "But when you start getting some of these bulbs that pull 200 watts, then we're starting to add up a lot of current," Overholser noted. The same case could be made for the existing wiring. The solution: "Use an auxiliary harness with relays that pulls its power directly from the battery source," he said.

A relay is nothing more than a very heavy-duty switch that does a lesser switch's bidding. A small electromagnetic engagement coil consumes on the order of milliamps means just about any switch can activate it. "The switch is merely a trigger at that point," Overholser added.

Though Overholser used the headlight switch example, relays and auxiliary harnesses have diverse uses. "The biggest consumption device in a car today is the electric fan," Overholser noted. "At roughly one amp per inch and double that during startup, we're talking some serious amperage." Hardly any switch can bear it very long and no thermostatic switch by itself can handle it at all.

We're being cute, but the debate isn't as Overholser's opinion shows. "I think the world of soldering," he said. "It's absolutely perfect-in a television set they never move."

When done properly both methods achieve the exact same purpose: They fasten the terminal to the wire and seal the wire so oxygen can't wick up the strands. But Fox and Overholser said their unease with soldering boils down to application. They said it's much easier for a hobbyist to affect a solid connection by crimping rather than soldering.

"If the wires are tied up right and someone who solders it does it for a living every day, it is fine in automotive," Overholser admitted. "But the typical guy buys a soldering iron. He's never had one before, but he starts soldering his wiring. He overheats the wires and they crystallize. He doesn't tie them up properly so they start breaking. And he just doesn't understand why.

"For the typical automotive application, a crimped wire is so much more reliable than a soldered wire," he continued. Fox added, "The thing is, with a good crimp tool you can crimp a wire and cover it with shrink tube and you'll have every bit as good a joint as soldering it." Want more proof? Until you open a radio, CPU, or switch, crimps are all you'll see in a modern car.

Overholser, Fox, and Logue advocate both bare terminals with user-installed insulation and pre-insulated terminals. "If it's underneath the car where it's in the weather then (bare terminals insulated with) shrink tube is by far better," Fox said. "If it's inside the body where you're hooking up taillights, an insulated terminal works fine." Overholser added, "A lot of it is just preference and appearance. A terminal with heat shrink is more attractive than one with a colored insulator, but both serve the same purpose." Rick Souza brought up another good point: "If you use a non-insulated terminal you can see what's there," he noted. "Then you just slide the heat shrink over it and you're done."

Whether or not you elect to solder, American Autowire's Michael Manning recommended crimping every terminal install. "Solder alone is not enough," he revealed. "A mechanical bond, generally in the form of a crimp, is the basis of any effective terminal installation," he instructed.

For years the standby wire insulation was Polyvinyl Chloride or PVC. Relatively tough, flexible, and inexpensive, it gets the job done, however, PVC is a thermoplastic. And like other thermoplastics like lacquers and synthetic enamels, it tends to oxidize and brittle with age.

Cross-linked polyethylene insulation is far more durable yet doesn't cost much more. It's a thermo-setting plastic, which means it has a molecular structure that cross-links into very durable chains. And like other thermo-setting plastics, like polyurethanes, it remains pliable and resists oxidation and abrasion to a far greater degree.

Cross-linked jacket also withstands far greater temperatures, whereas PVC begins to fail at 85 degrees C or 185 degrees F, cross-link can handle 125 degrees C or 257 degrees F. Now tell us what you'd rather have in your engine compartment.

Most cross-linked wire has a secondary benefit: more and finer strands. Since electrons flow along the surface of a conductor and not through the conductor, a conductor of equivalent size with more and finer strands can carry more current.

10. Protection is everything
No matter how advanced a wire's insulation, it doesn't stand a chance in a haphazard install. "Any time a wire goes through sheetmetal or anything like that, it should go through a grommet," Overholser instructed. Even though it doesn't conduct, he lumped in fiberglass just the same. "You know there are some sharp little pieces of glass in it."

The same goes for fastening wires to reduce their movement. A wire allowed to dangle on an exhaust manifold isn't long for this earth. Dirt and vibration conspire to wear through wire fanned out on a floorboard. More than one amplifier screw has self-tapped its way through stray wires.

Installers and OEMs alike go to great means to tie up wires and protect them from their environment. A few minutes of precaution here can prevent untold hours spent repairing a damaged system later on.