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Trailer electrical system maintenance is about more than lights alone

Posted: June 11, 2019 by Jim Park

TORONTO, Ont. — As trailers become more complex – thanks to onboard telematics and diagnostics systems, more auxiliary equipment, and more-sensitive electronics – maintenance demands will become more complex as well.

We are already running close to capacity in terms of circuits coming from the tractor, hamstrung by the limits of the traditional seven-pin trailer connector. But engineers are thinking beyond seven pins to 15 pins, and even self-supporting trailer electrical systems that can power auxiliary systems onboard the tractor.

That’s a bit of a role reversal, and it may be closer than you think.

How often do drivers report an ABS fault on the trailer, only to have technicians discover a lack of power from the seven-pin connector’s center pin? That pin is the only route for power to support the ABS system, automatic inflation systems, telematics, and more. At times there can be a lot of power traveling through that line, or not. If the fuse is blown, nothing on that circuit works. Or if the connector is badly corroded, voltages can be compromised, resulting in fault codes and poor performance.

Read: 5 Ways to Avoid Trailer Wiring Problems

“When someone says they’re having an issue with their ABS, or they can’t charge their lift gate, the first place I look is at that center pin,” says Gerry Mead, executive director of innovation at Phillips Industries. “Everything except the lighting comes across that pin. About half of the trucks I check for trailer electrical problems are hooked to tractors with a blown fuse or a badly corroded center pin.”

Corrosion on the J560 plug and the trailer pigtail is a big problem, especially in areas where a lot of road de-icer is used. The tractor end of that cable is hardly ever pulled out and inspected, tested and cleaned. Checking that connection is more important than ever with all the multiplexing and power line communications (PLC) data traveling back and forth along those circuits.

There are wiring solutions out there that will solve a lot of these problems, but some fleets are reluctant to try something new. Even with all the sealed connectors on the market, fleets still seem to prefer a metal plug on the J560 trailer connector, Mead says. “If it’s price, the extra cost for a premium connector is only about 10%. That’s not a lot to pay to reduce those sorts of problems.”

And Mead believes loads on the current connector will increase as more technology is added to the trailer, which will make corroding pins more of an issue going forward.

“The seven-way J560 is antiquated and we’re going to have to go to a 15 pin, the European standard, sometime soon,” he says. “It’s gotta happen. I mean, we’re used up. There’s a lot we could do with that 15-pin connector.”

Solar panels used to power various trailer systems could even be pushed forward to the tractor to charge batteries or power electric HVAC systems.

Caring for liftgates, APUs,  and more

Solar panels can also make a big difference for liftgates.

There’s one big problem with liftgates. They are usually at the back of the trailer, while the alternator is way up front. But a solar array on the roof could offer a direct path to power.

Liftgate batteries are typically charged by the tractor, but voltage can be limited by such things as an under-sized alternator and corroding cables. Those that travel short distances between stops may not be able to optimize charging without idling.

And trailers with short between-stop travel distances may not be able to optimize charging without idling.

Solar panels could solve many of those issues and save batteries from life-limiting deep discharges.

Bob Doane, chief technology officer with the solar energy provider eNow, says an American auto parts distributor saw a big difference in battery life after adding a small solar panel array to trailer roofs.

“AutoZone was replacing its flooded-acid liftgate batteries about every eight to 10 months,” he says. “We have had the solar panels on a group of test trailers for 30 months now and they haven’t had to replace a single battery.”

Not only can solar keep the batteries topped up, the associated electronics can optimize charging.

“We can put in all the current possible in [a] bulk charging mode until the battery reaches its optimum voltage of 14.2 to 14.4,” says Doane. “Then we shift to absorption mode, where the voltage is held steady, but the current is dialed back. That ensures the battery plates do not become sulphated through overcharging.”

It’s common these days to see tractors with solar panels on the hood and the roof of the sleeper. Montreal-based Groupe Robert extended the duty cycle of electric HVAC systems with the 600 watts generated by six flexible solar panels and four deep-cycle batteries. Duty cycles once limited to six hours were extended to 10 hours.

Imagine what an array two or three times that size on the roof of the trailer could do.

According to Phillips’ Mead, an electric climate control system powered by solar cells on the roof of a trailer costs less than half what a diesel APU will cost over its life — even less when you take maintenance into account.

“In my fleet days, I would keep a trailer for 10-12 years versus four to five years for a tractor,” he says. “That’s twice the payback time for the solar cells versus the tractor-mounted APU. And there’s literally no maintenance for the solar cells. Even if a few cells are damaged in a tree strike or something, the rest of the panel keeps working. With a 15-pin tractor-trailer connector, we wouldn’t even have additional cables to hook up.”

Trailer connectors that remain plugged into their sockets most of the time are not immune to corrosion. It may be even worse if you operate where corrosive de-icing fluids are used.

Electrical system maintenance

Until we have 15-pin connectors between tractors and trailers and current flow both ways between the vehicles, correct cable sizes and the state-of-the-art electrical maintenance will continue to be the keys to reliable trailer electrical systems.

Not to put too fine a point on it, most electrical maintenance isn’t rocket science. And let’s not confuse basic electrical maintenance with electronic troubleshooting, which truly is a science.

“Basic electrical maintenance may seem pretty basic, but it requires disciplined techs following proper procedures,” says Darry Stuart, a fleet maintenance consultant and frequent moderator at the Fleet Talk and Fleet Forum sessions during American Trucking Associations Technology and Maintenance Council meetings.

“It’s easy to take shortcuts, and since most techs don’t really like doing battery maintenance, you have to require them to do the work properly. Whether or not to disconnect the cables, clean the connectors, and load test the batteries should not be left to the technician’s discretion. That work has to be done at each and every PM. No ifs, ands or buts.”


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