5 ways to avoid trailer wiring problems

Jim Park
There’s more potential for trouble inside the J560 connector. Thousands are replaced every year due to poor maintenance.

TORONTO, Ont. — Until someone develops a cable-free electrical system for vehicles, we’re stuck with wires. And wires are generally not a problem until some outside force disturbs or damages them.

They are subject to chaffing from contact with nearby surfaces, or even from within the wiring harness itself, and the insulation can crack with old age. Once the insulation breaks open and moisture gets in, it’s all over but the shouting.

Corrosion will eventually eat right through the copper conductor, but the immediate problem could be a change in resistance. Sensitive electronics require precise voltages, and when you get a drop in voltage or an increase in resistance, sensors pick up the change in values and start throwing fault codes. That leaves your technicians trying to determine whether they have a faulty component, a faulty sensor, or a faulty wire. Troubleshooting such problems requires tons of valuable shop time.

“Corrosion in wiring can result in some very large diagnosis and repair costs, intermittent and frustrating circuit failures, frequent breakdowns, and premature component failures,” says Trent Siemens, director of maintenance at Paul’s Hauling in Winnipeg. “Fleets would be much further ahead trying prevent those problems from occurring rather than wasting time tracking the problems down and repairing them.”

Here are five tips to help minimize potential problems arising from wiring problems.

  1. Pay close attention to cable routing and possible sources of chaffing- and vibration-related damage during the truck’s pre-delivery inspection. Solve the problems before the truck goes into service, and if necessary, take the cable routing issues up with the OEM or the dealer to prevent future problems.
  2. Create a wiring repair policy so that all technicians repair wiring in exactly same way. There are procedures for repairing various sealed connectors supplied by the manufacturers. Follow them. If there’s dielectric grease or some other insulator inside a connector, make sure you refill the repaired connector.
  3. Establish a policy and procedure for repairing or replacing connectors. Don’t use non-sealed butt connectors. These are fast and simple but offer no protection from corrosion. Use soldered and/or crimped connections with double-walled heat-shrink tubing to seal and insulate the connection.
  4. Train your technicians on how to use multimeters and other diagnostic tools. Make sure they intimately understand Ohm’s law, battery load testing, parasitic drains, voltage drops and current draws.
  5. Finally, take every single probe-style circuit tester in your shop and grind the tip to a dull point. Make sure your techs clearly understand that they should never pierce wiring insulation when diagnosing circuit issues.



Jim Park

Jim Park was a CDL driver and owner-operator from 1978 until 1998, when he began his second career as a trucking journalist. During that career transition, he hosted an overnight radio show on a Hamilton, Ontario radio station and later went on to anchor the trucking news in SiriusXM's Road Dog Trucking channel. Jim is a regular contributor to Today's Trucking and Trucknews.com, and produces Focus On and On the Spot test drive videos.

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