I have a 77 f-250 with some fried wiring and I was thinking about replacing the main harness. I've always avoided electrical work as much as possible so I'm anticipating a challenge.

Aside from the OEM manual, do any of you FTE users have a recommendation for reference material to study before diving into this? Thanks y'all.

 

There is very little difference between early 70's (71/72) & 80's wiring.

Basically everything is the same until Fuel-Injection showed up.

It would be easier just to ask the questions pertinent to your problem.

Charging - is the same
Starting - is the same
Option wiring - the same


If you are wondering about the main harness underdash or underhood ...these are also generic topics.

Let's hear the problems you are having

 

Sink or Swim huh?
O.K. I'll jump in.

Basically I have shorts, how many I don't know. The truck starts and runs fine until the camper and running lights start to fritz out, then it dies. Normally it will start up fine after a minute or so.
There are visible wires with cooked insulation in the underhood harness as it crosses from passenger side to driver side. The lines are still hot. It has been recomended to me that I simply patch the problem areas. It's an illness that I have that makes me want to tear everyting out and start from new when I see a situation like this (at least on houses). I figure, in the amount of time it takes me to trace every wire and patch every short, I could replace the whole mess and hopefully get over my dread of electrical problems in the process. Whadayou think?

 

I think you are on the right track, would be easier and probably faster to replace than try to patch everything up. Plus for your higher current wires you can always run a larger gauge to help prevent the problem again. If you are familiar with House wiring, you truck will be easy, same principles apply, just 12VDC rather than 120AC.

Mike

 

Learning how everything works and how to troubleshoot elec problems is a good field to get into, and can probably even help on your house projects. The theory is the same, just the way things are done is a little different.

But, you don't have to know much about electricity to replace the harness.

If you find a restoration place that has your original factory harness, you just route it like the original and everything plugs in. They are not cheap though, if you can find one.

If you want to repair your harness, just carefully pull it out, lay it out on the floor, unwind all the wrap, and carefully pull the melted wires apart, cut them one at a time, and solder in new ones. If you are systematic in your approach and use a notepad to remember how everything goes, you should be successful.

What I would do afterward when you either replaced or repaired the harness, is install it back in the truck, paying special attention to missing grommets, and properly tying the wires up so they are out of danger. Then, instead of hooking the battery up, hook a 10amp or so battery charger up to the battery cables. Set it on 12 volts, and then start trying all the circuits in the truck(except don't try to start the engine). You know the wires are good since you fixed them, and any other trouble you may have will be evident when you turn that circuit on. The battery charger has a built in circuit breaker, and it will be tripped if there is a problem, and it will protect your new harness till you figure out what's going on. Hopefully the new or repaired harness will fix everything.

 

Thanks for the feedback guys.
I suppose it's a good idea to label the wires as to their component as they are removed, or is it maybe easier to note the component/wire color in the notepad? (Perhaps this is simply a matter of preference...)