Standardizing on a high-performance, high-quality trailer wiring system makes repairs easy.

Snapping in a new lamp or replacing a bulb might remedy a lamp outage or a flickering lamp aboard a trailer. But then again, it might not. Repair analyses show that half the time bulbs and lamps are fine, and that underlying causes are actually wiring-related -- either bad grounds, or damaged or degraded harness sections.

Since having operable marker, tail, clearance, and ID lamps is a safety requirement, being able to successfully troubleshoot trailer lighting is particularly important.

Correcting wiring problems can become quite labor intensive. In a worst-case scenario, a well meaning driver may decide to make a lamp repair on his own by using a butt connector to tap into a hot wire to get power. Chances are, however, he doesn't restore watertight integrity to the harness and neglects to tell maintenance about his handiwork. This is likely to create problems in the future. For example, if salt spray seeps into the repair, many feet of wiring will be ruined.

There's a simple solution to such problems -- but it involves foresight and spending money up front to save more later on: Upgrade from OEM standard to modular wiring.

The major elements in premium wiring systems are an outlet distribution module to which a series of individual marker, ID, stop/tail/turn and license lamp harnesses are attached with top-quality watertight connectors.

Modular systems not only direct power to all lamps from the tractor, but return to ground at tractor batteries through the seven-way connector. This circuitry is now being spec'd more often into new trailer orders. The cost? Approximately $125 to $150, including lights. (Standard lights and wiring costs about $80.) However, there's no reason why modulars couldn't be economically retrofitted into older trailers when original equipment wiring is in poor condition.

Phil Colgate, general manager of port operations for Chiquita Bananas, Wilmington, Del., is a strong advocate of modular wiring for his container chassis fleet. Modular wiring has all but eliminated the kinds of electrical problems that were common in the 1980s.

The carrier began spec'ing modular wiring in 1990 in 825 Strick chassis. Now, all 1,900 of its chassis are equipped with the premium systems, and Chiquita's wiring-repair costs have dropped to almost nothing. Much of the improvement is directly credited to the modular systems.

Most trailer OEM wiring, observes Colgate, is centrally grounded to a point on the trailer chassis. "This is a weakness in that it's a potential starting place for corrosion," he explains.

Chiquita's chassis utilize Truck-Lite's 87 Series Easy Seal modular systems (6-outlet distribution module). "The 87 Series gives us protection from corrosion that can travel forward along wiring paths," Colgate says. "Truck Lite provided spec'ing assistance and follow-up consultation. In addition, they periodically review chassis performance."

The 87 version that Chiquita uses is a 6-wire system to link each chassis' 16 lamps, 9 markers, 2 marker/ turn lamps on the side rails, 4 stop/ tail/turn signals in the rear, and 1 license lamp.

According to Colgate, the modular systems are essentially troublefree. "When the rare electrical problems occur, they are easy to remedy since they tend to originate in pig-tail connections that connect the harness terminations to the lamps themselves. He figures that the reduction of just one or two significant electrical problems on a trailer is more than enough to cover the cost of a modular system.

In the few instances where technicians had to work harder to resolve a tail or side-marker lamp problem, Colgate says it was necessary to remove the harness from the box and perform continuity tests of cables. "The boxes are sealed in cast epoxy, and technicians need to unplug the cable from the box and apply a tester to the pins. This takes very little additional time, and is actually a nice electrical problem to have."