So for some reason I felt the need to buy a 1988 F-150 with a 302 V8 5.0L about three years ago and fell in love with it. Well, recently I've run into some electrical issues. If I turn on all or most of the electronics like windshield wipers and sprayers, headlights, and the blower fan, the truck begins to buck like crazy. Also, if i have some electronics on and I'm waiting at a light or just at a stop, the blinker will begin to slowly stop blinking and eventually stop. I figured I had a low voltage problem and my first thought was battery or alternator so naturally I checked the voltage at the battery, first with nothing on and got a reading of 14.5V, which seems a bit high but the opposite of what I believe to be the problem. Then, I replicated the no blink situation and got a reading of 12.5V both when I tested the battery posts and when I touched the positive post and the alternator case. That should be enough to run the electronics but I still have the problem. So I took out the flasher and used my multimeter to test the voltage at the fuse box and got 11.4V. I also thought that I could rule out a bad ground by running my own ground. So, I ran a wire from the negative post of the battery to my multimeter and still got 11.4V at the fuse panel under the dash. It seems that the problem isn't necessarily a bad ground but a corroded or broken wire. Are there any wires more prone to corrosion or breakage than others? Also, is there anything besides a corroded or broken wire that could cause this? The issue seems to affect the whole electrical system and I'm at a loss. Any feedback would be much appreciated or even a wiring diagram.

 

I think you have a dying alternator. Go over to a parts store and get the alternator and battery load tested in the parking lot.