Tackling the Auxiliary Wiring…

…so that it doesn’t look like spaghetti.

I have worked on the wiring (among many other things) in a few cars before this. My first project was a 1983 F250 with a huge 460 V8. It was a beater, and it’s still sitting at my brother’s house. After that was a ’79 Celica (briefly), and then one of my favorites – the ’66 Mustang. Then a CJ7, the MG, and finally the Mercedes. What they all had in common was wiring issues of some sort, and I’ve progressively gotten better at keeping the wiring neat as I’ve worked on these things. I’m planning to do things a bit differently with the Mercedes. I intend to have a near-factory level of tidiness; I want the wiring to look like I didn’t just take some needle-nose pliers, crimps, and taps to the factory harness.

The Fusebox

I am adding a completely new and separate harness to the original harness in the Mercedes. I will leave the original factory wiring (almost) completely untouched. I will be removing unnecessary components from the engine bay, and I will have to do some work on the instrumentation in the dash and the tablet in the console, but I will otherwise leave everything alone. To facilitate this, I am adding a new fusebox and distribution busbar.

  • The fusebox with the lid attached. I had to assemble and wire it myself, but that took little effort. It's very sturdy!

Tools and Terminals

I used a few tools to assemble the terminals and butt connectors: three ratcheting crimpers, some wire strippers, and a heat gun. I used ratcheting crimpers to make sure the wires don’t come loose and have a good connection, and I used butt connectors with heat shrink and solder. For the relay and fuse terminals, which are pretty small, I used this crimper. For the butt connectors, I used this one, which could handle larger, more generic terminals. The Anderson Powerpole terminals were done with this guy, and I used these wire strippers to make clean and fast cuts. In regards to the crimpers, you may have noticed that the jaws are removable. You can get some with complete sets of jaws, but I opted to get more crimpers so that I wouldn’t have to be swapping jaws all of the time while working. If you don’t care about that or want to save a buck, these come with three sets of jaws.

  • This style of wire stripper makes for very clean and fast cuts. The jaws on one side grab the wire, and the other side cuts and separates the insulation. The yellow tab allows you to cut regular lengths of the insulation.

Protecting and Routing the Wiring

Once the harnesses are made, I will run then throughout the engine bay in wire loom. The loom will be fastened by clips every foot or so. The loom will serve to both protect the wires and keep things looking tidy.

  • This is basic split conduit. It will protect your wires from mechanical damage, and is often fire resistant to some degree. The wire is inserted through a split in the side of the loom.