Old Bronco/F-Series Trucks: An Efficient Electrical System

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By Mike Boyd

Old electrical systems can be a real
nightmare, especially if a previous owner of your vehicle modified it. 
There are some simple solutions to the headaches that poor wiring
First of all, start totally from
scratch.   Cut the original wires and purchase a newer F-150 or late
model Bronco electrical box from a wrecker.  These boxes contain eight
relays, fifteen large fuses, and seven standard fuses.   
Instead of tracing out each wire, strip out
all of the old wiring and the old fuse block.  Rewire each application into
the appropriate fuse in the newer F-150 electrical box.  Lighting and
electrical fuel pumps should be connected to one of the electrical relays. 
Older Ford systems used 18 gauge wire. 
Replace this thinner wire with 12 gauge wire for the charging system and 16
gauge for other electrical accessories.
When making your own electrical harness, use
electrical wiring tape or wire wrap to organize and compact these wire
bundles.  Purchase your wire in bulk and use the insulation color that is
closest to the original harness.  Keep the number of wiring splices to a
minimum.  This will prevent possible shortages and weakness in your
If any splices are necessary, solder these
connections and wrap the harness with electrical tape or heat-shrink
tubing.  You will clean up the appearance of your electrical system and be able to trouble-shoot electrical
problems simply and effectively.
I recommend that the electrical box should be
mounted on the passenger side fender well.  This will give you the shortest
distance to the battery and put the box at the highest point.  You will
also avoid the corrosive master brake fluid reservoir
and power steering unit.
The key to improving your electrical system is
starting over, using an electrical box that can easily be accessed on the trail,
and insulating the wiring with a sturdy wiring harness to prevent exposure to
caustic elements and abrasion.

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