I am working on a 77 f-100, swapped the body on a 4x4 frame. I cannot get any power to the fuse box except for the lights. Also no power to the ignition switch except for one wire that does not seem to do anything. This problem is driving me nuts, I cannot find a wiring diagram with all the parts on it to go off of. My chilton and haynes manual does not have the right diagram, and the shop manual does not have a complete wiring diagram. Does anyone know where I can get one, or have a clue for this problem. It's a 77 f100 ranger with a/c. Thanks for any help.
that was the first thing I checked, I have all 3 of them on there and even cleaned them up nice, then checked the voltage before and after the fusible links to make sure they were ok. I wonder if the power might go to the fuse box throught the air conditioning harness, this wiring is a pain in the butt.
I am sure the fusible links feed the fuse box and the ignition switch...........if you have voltage on each side of the link try a few feet up the wire.....maybe the links are blown and you are measuring before the "open" part of the link.
Maybe ensure the grounds for the cab, engine, etc are good... could be the voltage is available but there is no ground????? Just a guess though.
Are you positive that all the connectors are hooked up......been a while since I worked on those "new" 70's trucks
I traced the wires, one of the fused wires ends up at an a/c connection, and the other goes to the lights, which work. It's tough to figure it out without an accurate wiring diagram. All the grounds are good, checked them out. When I bought the parts truck you had to start it from the starter realay so I'm not sure what the problem would be.
Another thought....... try another ignition switch if you have one... you said there was power to one wire so....... it may be the power feed to the ignition switch that feeds the fuse box when the key is on......but if the switch is dead...... no path for power
This diagram shows a black/yellow going to the ignition switch. There is usually a splice along the way where it splits and also feeds the fuse box. If you can't find the black yellow at the starter solenoid, then start at the ignition switch and look for a black/yellow and work your way back.
that is the same diagram I have been using, and alot of the colors don't match, and alot of the parts don't match, and the a/c option seems to change alot of things. All of the larger wires that you would think feed the fuse panel run to the a/c parts, they seem to turn into a bunch of small wires, then back into the large ones that run into the fuse panel. I think the black yellow wire ended up going to the a/c, I have power to the interior and exterior light part of the fuse panel and that's it. I think I just need the correct 77 diagram, that one on the autozone site is the same in the chiltons and haynes manual, and it lists for 73-78, I know there were changes in there, it's to generic.
Couple more thoughts
You say the large wires go to the ac plug and then turn into small wires and back to large wires....... so any chance those small wires are fusible links????
If you have power to the "always hot" parts of the fuse box, lights, then it appears you are missing the switched circuits....... so these are controlled by the key/ignition switch............. so a large wire to the switch should have 12 volts on it that is "switched" to feed the other large wires that feed the fuse box in "acc" and "run"..................... so if that voltage is missing I guess you have to start tracing wires................. no fun in these trucks.....especially if there has been some well intentioned wire mods done by PO's
Thanks for that link, I was looking for one of those. So the fuse panel, other then the lights, is wired through the ignition switch? I was thinking that, Now I just need to know where the wires are supposed to come from. I think I have found all the fusable links, but I think ford liked to hide a few that are hard to find in the dash wiring. I will do more checking this weekend, and hopefully I'll have my diagram soon. The harness looks other then a radio un mollested, kinda suprising for a 77, but It was a gov. truck for a long time so it probally sat most of it's life. Thanks for the help, I'll report back when I find something, and keep the ideas coming, they are a big help.
Some of the fuse box is fed by the ignition switch. The stuff that only works with the key on like the radio, the heater blower, the turnsignals, etc. The rest of the fuse box is fed by the same wire that feeds the ignition switch. This is for stuff that works all the time, like the brake lights, dome lights, marker lights, etc. The headlights have their own seperate feed directly from the starter solenoid.
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