At Monaco Coach Corporation’s Plant 66, a bustling assembly-line factory in Bend, Oregon, just 125 miles east of corporate headquarters, you’ll find a highly-skilled team dedicated to creating the wiring harness assemblies for the firewall, dash and transmission of the Roadmaster Chassis. Also known as Electronic Design and Assembly (ED&A), this quiet division of Monaco Coach Corporation is making a resounding impact. Plant Manager Wes Murphy gave us a tour of the facilty and explained some of the details behind the process.

“We build to order,” Murphy explained. “This allows us to customize all the specials right into the original harness.”

The process of creating a made-to-order wiring harnesses starts in a parts room filled with terminals, connectors, wires and ties all neatly organized along rows of tall shelves. “We begin with a coach number and an order form,” Murphy said. At this stage each harness is assigned a part number to identify the individual specifications. “This helps for future reference in the event of maintenance or repair to minimize down-time,” he added.

Next to the parts room is the first station on the assembly line where large barrels of wire spools thread into a large glass encased machine. At this juncture the wire is cut a pre-programmed length, each end is stripped and terminals are attached. The machine also labels every three inches for quick identification of what each individual wire controls.

Once cut and stamped, the wire is then neatly wrapped and sent over to a pressing station where large vise machines are lined up along benches to use in attaching various connectors to the wires. The connectors are waterproof, but moisture can occasionally find a way to penetrate, so as a side note, refrain from directly spraying water onto the wiring harness when you’re washing your RV.

After the connectors are attached, it’s on to the next stop, rows of chest-high boards dotted with large hooks to hang the wires, while assembling the actual harness. The flat work surfaces rest on hydraulic lifts, and floor pedals conveniently situated up and down the line make it easy to raise or lower the workspace on demand.

A technical-looking diagram outlining the wiring specifics for each harness is taped in place on top of the board for reference by the assembler in constructing the harness. This electrical roadmap would take many of us hours, if not weeks, to decode, but it’s all in a day’s work for the men and women fabricating each harness, and without missing a beat, they weave the long wires back and forth along hooks lining the boards. Because the harness can run up to 45 feet long, the wiring is assembled in a figure eight to save some assembler mileage as 75 to 100 wires are joined together to create a complete harness.

White automotive wire is utilized due to its high temperature ratings and resistance to oil and gas. Plastic black tubing called “Loomex” is wrapped over the wires of the assembled harness. This black material is durable enough to protect the wires, but can still be easily cut to expose the ends. Loomex will also help to reduce the chance of rodent damage to the harness, but only when you take the appropriate steps to prevent rodents from entering the RV in the first place. “This includes traps, sealing access points, and storing your vehicle on solid surfaces like pavement or concrete instead of grass or in a field,” Murphy explained.

Next is the testing stage where the wiring harness is connected to a scanner that determines whether each wire is operating as designed, and if not, pinpointing the exact problem. As soon as the harness gets a green light, it is time to move on to the final step. “We wire the dash panels,” Murphy said, holding up a panel with gauges and buttons intact. He points out a sticker on the backside of the panel identifying the part number of the individual wiring harness. The firewall harness, which is used to connect the dash assembly to the rest of the RV, is carefully wrapped and labeled to ship alongside the dash panel.

Plant 66 employees assemble an average of about twenty harness assemblies per day and none of them sit around long enough to gather dust. Each afternoon a line of carefully-wrapped pallets are shipped off to Monaco Coach Corporation’s main assembly plants in Oregon and Indiana. Once they reach the intended destination, the harnesses are installed in the RV to control the dash gauges, transmission, coach electronics and exterior lighting.

Access to the harness after installation is generally gained at the dash area or through the front and rear run boxes. Murphy has a short list of tools you should keep on board to help with troubleshooting and repair of the wiring harness — a flashlight, inexpensive multimeter, wire strippers/cutters and a pair of crimpers. He also proposed that you carry a pocketknife to carefully cut electrical tape and Loomex. For more advanced repairs, Murphy recommended a soldering iron. His suggested list of spare parts includes fuses, electrical tape and a modest selection of terminals and connectors, “ring terminals, male and female slip-ons and butt connectors.”

There are a few steps you can take to troubleshoot a wiring harness. Start with the obvious, such as a blown fuse or burned-out bulb. Follow that up with a visual inspection, looking for wires that are pinched, cut, chaffed, discolored or deformed. “Deformed wires can indicate that the conductor is broken underneath the insulation,” Murphy said. Gently wiggle and pull on connections, terminals and splices to locate possible loose connections. If any wires need to be cut or replaced, Murphy offered a word of caution: “One wire at a time,” he said. “More than one wire at a time will briefly short all the wires together, which could cause more severe problems.”

A lot of time and effort goes into creating the wiring harnesses at Plant 66. Along with a finely-tuned product, you also get a carefully-documented series of checkpoints to assure speed and efficiency in the event of future troubleshooting and repair. While some may not rate a wiring harness as one of the top ten reasons to buy a particular brand of motorhome, it’s the skilled and professional behind-the-scenes attention to detail that helps keep Monaco Coach Corporation and its Holiday Rambler RVs the best in the industry.