Short story: Lots of aftermarket stuff added. It happened over years. Each new thing was a new adventure in splicing which created a wiring and troubleshooting nightmare. After a lot of planning I spent the weekend cleaning it all up and documenting every splice, connection, wiring route.
I have a center console so I decided to remove the glove box and instead install an aluminum bracket for some electrical bus bars.
Previously I had used 3M wire taps for each additional component. (BTW, if you go this route, use the 3M stuff it is far superior to what you will find in the local auto stores).
It got out of hand. I had no idea what was tapping into what. Time to clean it up. So I purchased a couple of bus bars and went to it.
The aluminum bracket Doubles as a ground plane. Goodness that's a lot better. I drilled and tapped into it for the ground connections.
Here's what it looks like.
Not as clean as I wanted but I have every single connection documented. I needed to leave a bit of slack in the wiring in case I had to unbolt the bracket to get what is behind it, so I couldn't make it as tight as I would have liked.
The bracket has a V on both ends that match the dash. This helps keep it from moving around. It is very secure.
I ran an 'always' hot to the smaller bus bar. I use a relay to energize the larger bus bar. I use the "AUX" port on the fuse box to signal the relay.
The small device seen at the drivers end is a 12v to 5v contraption. This is used for the digital voltage meter but might get a second purpose to run the stock gauges.
There is some room left over for another bus bar for illumination of the aux gauges. I predrilled/tapped for the bracket.
Here's some of the mess I removed:
Yes, there are at least 5 wire taps, a couple of extra relay's I didn't need and so much extra wire.
My approach: I documented what I wanted to do ahead of time and moved each component to the new system. Some folks just 'cut it all out and start over', which is a valid approach. I decided to painstaking move each circuit to the new system. I tested each new circuit and each previously moved circuit as I progressed.
I am very excited to have accurate documentation on all of these additional circuits.
Here is the list:
Stereo: Stock was Aux only but modern stereo has constant power for memory and aux for normal operation.
Aftermarket gauges: Fuel pressure, tach, trans temp
Dual battery switch: Allows for adding second battery into the system when aux on, always or off
Digital volt meter: ON/OFF or Aux on. Also select which battery is displayed
Ham radio
CB radio
ARB compressor for axles
Compressor for filling tires
Refrigerator circuit
Electric fuel pump
Stereo amp
High idle carb solenoid
USB ports for charging