Log in

View Full Version : Car Wiring 101



Dondero14
01-03-2026, 05:16 PM
I know a lot of people on here have worked on cars previously and/or have a very great knowledge on them to begin with. I, for one, am as green as the grass in Ireland when it comes to car wiring. I've never done it and I'm sure there are probably many out there that may be in the same situation. Having started my wiring harness on my car, I've started taking some time to learn at a basic level how the electrical system works in a car. The biggest thing I didn't fully understand was why there were so many grounds throughout the whole wiring harness. What I didn't know is that the chassis is being used as a conductor back to the negative battery terminal. That was the lightbulb that I needed to fully understand the bulk of this topic. I know how electrical components function and work but I just didn't fully understand all the ground. After I learned that, everything else made complete sense. I found two incredibly good watches on youtube that dumbs the process down significantly and I figured its worth sharing. If one person reads this post and gets something out of the videos below, I'm happy to know I was able to help them better understand this portion of the build because they simplified a lot for me.

This video explains very well how all the electrical grounds work within a car
https://www.youtube.com/watch?v=gC69-BDzvps

This video shows how a basic simple electrical circuit works for a car. Ironically he is driving a F5 Cobra.
https://www.youtube.com/watch?v=CzVraj_aL54&t=1s

FLPBFoot
01-04-2026, 08:39 AM
Good stuff. If you look at the Ron Francis harness there is only one connection point from all the harness to the chassis. It is recommended practice to connect the front and rear harness black ground wires to the chassis. I spliced into the front harness ground wire and tied it to the frame up on the 3/4" tube along the side of the engine bay. Also spliced into the rear black ground wire in the rear harness and tied it to the frame back above the rear axle. This was recommended practice from build school.