Adding New Circuits

[banjopicker66]

I have been working on ideas to add additional and more robust circuits to my Slick without hacking up the original wiring. My purpose is two-fold. First, I want to add circuits for high power things like electric brakes, high wattage backup lights, radios and the like. The original wiring is intact for the most part, but I do not want to overload the factory ignition switch and fuse box to carry the additional current, but instead want to add an additional fusebox. I am not going for a purist look, so the under-hood fusebox seems to fit the bill.
Also, I want to add a disconnect between the firewall and the extra under-hood wires. There are additional wires for gauges, a tach, electronic ignition etc etc and I want them all collected into a single (or dual) multi-point disconnect to allow for easy disassembly, troubleshooting and so-forth.
One solution that I just couldn't make work was the later model under-dash fuseboxes, as they mounted to odd-shaped dash brackets and weren't really suitable for the under-hood environment.
I think I found the answer. The pictures below are of the underhood wiring harness from a '93 or '94 F-150 with a 302 and automatic. The fusebox itself came from under the hood, has high capacity fuses, regular fuses and relays, all in a nice box with a cover. It sits in a bracket that mounts with 3 studs to the inner fender. Nice and neat.
Note the long length of wiring to the left, which is the power supply from the battery to the fusebox. This will allow me to supply power to the fusebox directly from the battery, as I intend to site this on the driver's side of the truck on the level section of the inner fender. Note that a lot of the wiring will disappear once I dissect it all out - this is how it came from out of the truck. (I will use the running light sockets as test lights, too. Waste not want not!) Anyone want the bulkhead or computer connector?
There is a multi-point connect affixed to the same bracket. It fed the engine components such as the injectors, and I suspect most of the wiring will come from the computer connector, but wiring coming through the firewall can be spliced into this connector (with spares leftover for future use) , thus giving me the disconnect I need. I just cut the wires right where they joined to the injectors - too much trouble in 100 degree heat under the sun to take it all out.
This cost me $5 at the local pick and pull - well worth it I think.

Complete harness:
http://fordtruk.com/forums/album_pic.ph ... user_id=48

Fusebox closeup:
http://fordtruk.com/forums/album_pic.ph ... user_id=48

Bracket and multi connector closeup:
http://fordtruk.com/forums/album_pic.ph ... user_id=48

[Brian Taylor]

On my 66 the original fuse block was brittle. I bought a new style blade fuse block and cut off my old one and wired the new blaock to it. My wiring is still in good shape. Later I bought a second one and wired it to a relay and made the entire set of fuses ignition hot to run my later additions of power windows, seats, amp, AC etc.
Not as drastic as a new harness and still a clean set up.

[banjopicker66]

Here is the harness all cleaned up, with only the relevant circuits remaining. All of these come from the fusebox.

All tidied up with extraneous (non-fused wiring) out of the way. Note the many-wired main disconnect at the top, behind the fusebox:

[albumimg]9230[/albumimg]

Here is a closeup of the wiring out from under the fusebox, it includes a number of wires for relay controls, as well as power fused supplies.

[albumimg]9231[/albumimg]

The underside - note that some relays are already wired up internally.

[albumimg]9232[/albumimg]

[oldfordcoupe]

i got the relay box out of a explorer to supplement my orig. sys it works out great

[banjopicker66]

Progress Update, Relays:
There are 4 existing SPST NO relays with 5 sockets, but only 4 are wired up. I can easily add in the extra wires if needed, of course.
I will use 1 relay as a RUN - ON relay to turn 2 other ones on when the key is at RUN. These 2 relays will supply power to the electric brakes and to the electronic ignition.
The third relay will supply juice to a set of halogen backup lights. It will be wired to turn on the lights when I ground out the switch - in fact, I'll use the the existing horn relay and wiring to do this.
Each relay is powered internally (under the fusebox) by a separate, fused circuit, by the way, so the heavy duty current will be protected as well as the control circuit.