Wiring, Connectors & Lights
Aggressive road salts require a more focused look at corrosion and how to beat it.
Tom Berg
Equipment Editor
Electrical problems consistently top the list of the most troublesome items on any truck, and the problems have been aggravated in recent years by highly corrosive chemicals spread on pavement to melt snow and ice. Common salt – sodium chloride – was bad enough through the years, but magnesium chloride and calcium chloride are worse, attacking anything on the chassis made of metal, including wiring, connectors and lighting fixtures.
While traditional salt becomes somewhat inert as the road environment dries out, the new salts remain continuously active by absorbing moisture from the air in a process called “deliquescence.” The salts are insidious, creeping into every nook and cranny in vehicles and sticking to whatever they touch. And they’re not easily washed off, according to discussions heard during meetings of the Technology & Maintenance Council of ATA.
The aggressive corrosion is especially hard on today’s increasingly complex trucks, said Brad Van Riper, vice president of research and development at Truck-Lite Inc., in a presentation to a Society of Automotive Engineers audience. Trucks have hundreds and sometimes thousands of electrical and electronic circuits which are often interdependent.
Corrosion increases resistance to current, keeping needed amperes from reaching everything from the starter motor to anti-lock braking systems. Some wiring systems are multiplexed, and the low-voltage coded signals that run through them can be interrupted by even small amounts of corrosion anywhere in the harness.
Road authorities are giving the prevention of collisions higher priority than damage to vehicles, and don’t plan to cut use of the new salts. Political pressure and the wrath of motorists, whose personal vehicles are also attacked by the chemicals, may cause change in the future. But for now, truck operators must focus on solutions. Among them:
• When ordering new trucks, tractors and trailers, specify top quality electrical products that are sealed against the ravages of moisture and salts, and see that they are installed intelligently.
• As part of regular maintenance, inspect wiring and connectors closely, looking for any signs of corrosion.
• When repairing electrical parts, use supplies and techniques that retain the integrity of the sealing materials.
• Insist that wiring for truck bodies be plugged into special chassis connectors. Don’t let body installers cut into chassis wiring to get power for their lighting.
DURING SPEC’ING
Wiring systems on power units are set up by factory engineers who have responded to truckers’ concerns with improved designs, such as making connectors more secure and getting them out of the path of splash and spray. When considering a new or used truck or tractor, ask colleagues who already use that make and model what their experiences with the wiring system have been. Study the wiring designs and the apparent quality built into them, and ask the dealer sales person or factory representative how the designs and materials fight corrosion.
Ask what electrical options are available on a new truck. Selecting light-emitting-diode lights, for example, is wise because LEDs use one-tenth the power of incandescent lights and are therefore less susceptible to reduced current due to corrosion. This also makes more voltage available for other uses. Plus, LEDs should last 10 times longer than incandescents.
Any problems with a truck’s basic electrical designs can be caught in a fleet’s pre-delivery inspection of the “pilot” vehicle shortly after it comes off the line, Van Riper says. This is the fleet manager’s chance to spot potential troubles before they are repeated on subsequent vehicles in the order, and some ask supplier reps to go to the reviews. They can see how their components and systems are installed and suggest changes.
Truck manufacturers will correct design flaws if they can, he says. For instance, wiring that’s stretched to connectors can be hard to work on later An inch or two of slack at each connector will later give the mechanic room to cut corroded material from wire ends and reattach them to the connectors.
You have more choices in the electrical components that go into a truck body and trailer. All vehicle manufacturers have standard systems, but they sometimes have to cut corners to keep selling prices down for short-sighted customers. Higher-end trailer and body makers make better systems standard. Opt for a higher quality system because, while you may pay a few hundred dollars more now, you’ll save thousands in maintenance expenses and an untold measure of grief over the vehicle’s life.
SPECIFIC ADVICE
Van Riper, a long-time active member of TMC, says he culled some methods used by aircraft designers for their electrical systems because they’re also usable in trucks. Truck-Lite and its competitors, Grote, Peterson and Phillips, all offer premium products that put these ideas into practice. Among them:
• Use hermetically sealed connectors designed to block entry of moisture Metal parts are “potted” in urethane or other materials, so they can be immersed in water and still work. In non-sealed connectors, apply dielectric grease to displace moisture and promote conductivity.
• Avoid connectors with top-mounted lids through which moisture can drop.
• Mount connectors in a protected place on the vehicle, and avoid spots where water can collect. If they’re located outside, for instance under a trailer, connectors should have sealing covers to deflect spray, or boots that can be sealed with adhesive.
• Mount connectors horizontally so moisture drops harmlessly off their bottoms instead of running toward seals and joints, which it will do on vertically mounted connectors.
• Put loops into outside-hung wiring so moisture has a place to collect and fall off. Never allow exposed wiring anywhere in the vehicle.
• Use couplings of the same metals; electrolysis between dissimilar metals results in additional corrosion.
• Don’t put side loads on connectors. This drains power and introduces more opportunity for corrosion.
• Don’t allow the use of hygroscopic materials – anything that absorbs moisture – near electrical components. Some plastics are hygroscopic, and some gasket substances used in grommets are, too.
• Be aware of any fluids that may come in contact with connectors and other parts. For example, a mechanic can spill windshield washer fluid onto an underhood connector box as he refills the reservoir.
In speaking to vehicle builders and makers of electrical components at the SAE meeting, Van Riper said, “Seal everything and use everything sealed. Use potted circuit boards to minimize corrosion. Use materials in your designs that are as corrosion-resistant as you can afford.”
