There are a few things I would not have attempted when I was a mechanic. One of the most troubling things I was tasked to repair was the electrical system. When I started working on trucks I had not been around them much and worked on them even less. I had been a mechanic on irrigation engines, John Deere equipment than to the Ford garage; at each of these shops, I learned that I really enjoyed the challenge of finding and repairing electrical problems.

Thru the years I have done complete rewires of many semi-trailers, custom cars and solved issues that the local shops couldn’t. I still enjoy curiosities and field phone calls answering questions about tricky electrical problems. I have always had a small toolbox that only had “stuff” I needed to do the repairs of an electrical system. Fast forward to today.

The electrical systems of the trucks today cannot be attacked as I did 20 years ago, in fact, most of my tools are only relevant to trailer light repair today. I will say that I believe the wiring harnesses of today are more efficient and trouble-free than yesteryears harnesses. That brings us to the box I carry for electrical repair.

Do not pierce any wire that you do not intend to reseal in some fashion. Any time you pierce the insulation of wire the possibility of moisture entering that piercing is tremendous. Using a Test light on any of the trucks wiring harnesses could damage the electronics that run all the trucks systems. A volt/ohm meter, digital, not analog, is required and a good flow chart of how to find a certain issue is required. Not following the flow chart can again cause damage and create problems that you didn’t start with. My advice is to stay away from the trucks circuitry, have the folks that have the training do the repairs.

Trailer and box lights are different to me as once the power has left the truck to the lights it is 12 volts, positive and negative. If there is a light out the first thing I do is change the lamp, that will usually solve the outage. If there is no change I look for broken wires, anywhere that debris could hit and damage a wire to cause corrosion or just pinched it in two. Making repairs is fairly simple, you must understand the tools and connectors and use them properly to get a good repair.

Having the right tool and parts on hand can save you much time and money. When I drove for a major fleet I kept spare lamps in the truck just in case I found a light out, change it out and be on my way. The only electrical components I do my own work on now is lights, known component failures and batteries, everything else goes to the shop. Think about what you are getting into before you get too deep but repair what you can if you feel confident enough.

Till next time, be safe out there.


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