The U.S. Department of Transportation mandates red and amber lights and headlights  in these respective areas on ready-mix trucks.
The U.S. Department of Transportation mandates red and amber lights and headlights in these respective areas on ready-mix trucks.

In many areas of the country, more than 30 percent of pours happen at night. The last thing a fleet manager needs is to learn of a truck inspection by a zealous policeman while on the way to a jobsite.

Along with all the other rules you need to know, there are two guidelines for adequate truck lighting. Federal Motor Vehicle Safety Specification 108 requires certain lighting be on all commercial vehicles. Federal Motor Carrier Safety Regulation 49CFR393 Part B states, “All lamps required by this subpart shall be capable of being operated at all times.”

Problems with lights and wiring were the second highest maintenance cost, right behind tires, the Truck Maintenance Council (TMC) reported a decade ago. Lights fail from physical and chemical damage, shock and vibration, burnout, and low current.

Now that most TMC manufacturer-members have adopted sealed harnesses and LED lighting, wiring problems no longer make the top 20 list. “Lighting is just not an issue anymore,” said one member.

Despite advances in wiring, many mechanics continue to use individual bundled wires leading to each lamp, with ground wires going to the frame. This is cheaper initially and easier to fix when repairs are needed. But in the long run, they can be more of a problem than a solution.

A sealed system has a jacket molded right onto the wires and connectors. It is not just a cover; it's a structure. Grote's Ultra-Blue Seal Lifetime Harnesses, Peterson's Maxi-Seal Harness Systems, and Truck-Lite's Series 88 harness systems virtually eliminate wiring problems.

Corrosion issues

Modular sealed wiring fights corrosion. Coupled with sealed and LED lighting, modular systems can reduce overall ownership costs by eliminating the need for repairs. If you plan to keep a truck longer than four more years, it will probably pay to upgrade to sealed harnesses.

This is true if you are working in areas where using aggressive snow-fighting chemicals has increased the severity of corrosion on truck chassis and components.

To keep lamps operating longer, regardless of wiring, never start a truck with lamps turned on. Surge currents can vaporize filaments on incandescent lights.

If a lamp appears to be burned out, check it with a lamp tester. Recently, the top three lamp suppliers reported at TMC that more than half of the lamps returned as defective still worked. Customers not only wasted money replacing those lamps, they also missed the underlying causes of the failures—usually the wiring. Then they had to repeat repairs.

For those whose fleets have not been equipped with sealed harnesses and still have the old-style wires, here are a few tips to help care for discrete wiring.

Look for corrosion at terminals. Trailer nose boxes, 7-pin plugs and sockets, and all connecters are extremely vulnerable to corrosion. If you have a particular problem, I've found that Phillips Industries has J-560 plugs and boxes with replaceable parts that make repairs easy and isolate any corrosion that occurs.

Check the wire damage and any splices for openings that may allow internal corrosion. If wires go through holes in chassis or body parts, make sure the frame grommets are in use and in good condition.

Examine the ground wires to the chassis, and replace any corroded or damaged parts. If the chassis is corroded where the ground connects, clean it with a wire brush and emery cloth. Then, reprime, repaint, and reattach with new connectors. It's a good idea to paint over the connection with liquid vinyl, sold in parts and hardware stores as electrical tape in-a-jar. It will retard further corrosion.

If you need to replace connectors, cut wiring back at least a half-inch from the end. Inspect the strands to be sure moisture and corrosive salts haven't migrated between wire strands. Be sure you have enough wire to allow a connection with enough slack so that no tension is on the wire. In areas subject to splash and spray, include a downward-pointing drip-loop to let excess moisture and salts drain away. Avoid arches that allow them to flow into sockets and connectors.


You can help your cause by buying replacement lamps with molded plugs or sockets, rather than those with wire pigtails. That avoids the need to splice wire. You can protect plugs and sockets from corrosion with dielectric grease. Grote Ultra-Seal Corrosion Protection, Lubriplate DSES, and Truck-Lite NYK Grease are available at most parts stores and truck dealers.