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Modern Trucking Techniques

LL’s technical editor goes to the industry experts to offer valuable tips on care and maintenance of your rig’s wiring system

by Paul Abelson, technical editor

If the engine is the heart of today’s truck, then surely its wiring is the nervous system. Wiring powers lights and accessories, and in modern vehicles, does so much more.

Signals from sensors run through wires. Systems like ABS are activated through wiring. And climate control and driver-comfort accessories get their power and control through wiring. Clearly, the care and maintenance of wiring is essential to the smooth operation of any truck.

So I could get it all right, I turned to two widely respected industry experts. Brad Van Riper is vice president of research and development for Truck-Lite Co., a leading supplier of safety lighting and vision systems. Carl Smith is vice president of sales for Sure Power Industries, a leading behind-the-scenes supplier of wiring devices used by virtually all the truck manufacturers.

Both Van Riper and Smith are heavily involved at The Technology and Maintenance Council, where they helped create all the recent Recommended Practices dealing with wiring. They are both frequent panelists and presenters at the Society of Automotive Engineers annual Truck and Bus meeting.

Wiring’s greatest enemy is corrosion. That’s probably true for the entire electrical system. With today’s snow-removal chemicals and other uses of chlorides, you must protect wiring from these salts. Whenever metals come in contact with moisture and chloride salts, corrosion occurs. Iron-, aluminum- and copper-based metals all oxidize, and oxidized metals raise electrical resistance significantly. Corrosion can create short circuits that result in incorrect signals being sent to processors, causing malfunctions.

The new snow-removal chemicals, magnesium and calcium chlorides have another property. They are deliquescent. That means they have the ability to liquefy by drawing humidity from the air. They may be relatively new to snow removal, but they have been used for years to control dust. You don’t have to drive on dirt roads to be exposed. Just driving near them can be enough to expose your truck to these salts.

Depending on where you operate, chemical corrosion can be a year-round problem, but one that can be solved.

First and foremost, keep the underside of your tractor and trailer clean. Power wash your rig. Then practice good wire maintenance. Keep wiring sealed. Never probe through insulation to determine if current is flowing or to take measurements. Even the tiniest pinhole can be a conduit for salt-laden moisture. Do your diagnostics by removing wires at the connectors and touch your probe to the exposed metal. When you’re done, use dielectric grease if called for and plug the connectors back together.

Truck-Lite’s Van Riper suggested these “DOs” and “DON’Ts” when working with truck wiring:

Electrical systems have improved over the years. You should take advantage of the improvements whenever working on your lights or wiring. For example, light emitting diodes (LEDs) have come down in price. They pay for themselves more quickly in longer life and lower maintenance cost. If you are still using bulb-replaceable lamps, at least switch to sealed lamps with modern plugs attached instead of using chassis-ground wires.

The newest wiring systems from Truck-Lite have triple-sealed plugs that do not require dielectric grease to keep moisture out. Their Series 88 harness can be ordered with sealed modules that eliminate the need to wire a trailer nose box. Just plug the modules together and you get a perfect connection from the 7-pin cable through the trailer.

Installing and adding new wiring
There are times when you need to add new wiring to power or control new accessories, such as inverters, refrigerators or any of the comfort and convenience devices now available. Sure Power Industries’ Smith offered some tips on adding new wiring.

First of all, don’t use a single 12-volt power outlet to power half a dozen devices. We’ve all seen cabs with multiplier plugs plugged into multiplier plugs, with huge loads running through just one outlet. Most lighter sockets are designed — and fused — for a maximum of 10 amps, or 120 watts at 12 volts. That’s fine for a CB radio, a small cooler and perhaps a cell phone charger, but there are limits as to what can be run. I’ve seen drivers who kept blowing their 10-amp fuses, so they replaced them with 30-amp ones. That’s pushing the limit of the wiring, and could result in melted insulation or even a cab fire.

Anytime you want to add a major direct current (DC) appliance or accessory, install a dedicated circuit, or else consider getting an inverter and using household alternating current (AC) appliances. When getting an inverter, make sure it is sized (and wired) to handle all the appliances it will power. Keep inverters as close as possible to the batteries, and use very heavy-gauge cable to handle the current. A 1,500-watt inverter with 20 percent inefficiency can draw a steady 150 amps, with surges doubling that. That’s why many manufacturers call for 4/0 cable from the batteries.

According to Smith, here’s the proper procedure to follow when installing and wiring-in add-ons:

I’d like to add one more piece of advice. Whenever possible, err on the safe side. Use heavier wiring, never lighter. Use wire with thicker insulation, never thinner. Space your cable ties closer. Keep in mind why wiring fails and how to wire successfully, and you’ll avoid many common problems.

Paul Abelson can be reached at truckwriter@netscape.net.