Okay, so I've been fighting this electrical issue for a while and I'm at my wits end! Hopefully someone here will recognize my symptoms and offer some insight, so here ya go:

started summer last year. I was installing an aftermarket radiator fan and bronco wouldn't start. Window's wouldn't go up. Guages pegged out. After messing with it for two weekends tracing wires, friend came over, messed with something under the dash, back up and running. Drive it like this for another few months without problems. Starts again. I can get it to start, but it won't run above idle. Guages peg out, and Speedo pegs down (below 0), windows won't work, red 'engine' light comes on a little. Also, sometimes the truck turns over continuesly on it's own without even the ignition wire on the starter solenoid, I have to pull the battery cable to get it to stop. Sometimes I got little shocks while working on the truck while touching the metal. I've burned up a couple of starters as well.

Here's what I think is the situation: It seems like the truck as jumped to a 'safe' mode, where it will run, but not correctly until the problem is fixed. Personally, I think I have power to ground somewhere. I am suspecting something under the dash, as one of the P.O. did some of their own wiring under there.

I'm posting here incase anyone has any other thoughts on this.

Specifics:

88 Bronco, 302. Some custom work, but nothing with the electrical really except I installed an aftermarket chip that goes inbtween the wiring harness and the computer but I stalled that after the problems started as I got it with a used computer from a friend trying to see if the comp was the problem.

Any help would be appreciated.

 

On the face of it I would say.....give that friend of yours that cam over the last time, and have him duplicate whatever he did under the dash the last time that got it running right again.

Or......take a good look at ALL the battery leads, their respective terminals and hardware. Make sure that all ground connections are clean and tight.....if that dont cure the problem start working your way back from the battery.

 

My 92 had several wiring "conditions" that the P.O. had "left" when they parted with the truck. Not the least of which was a HOT power feed for some sort of (what I consider useless in a truck) audio peripheral UNDER the front seat! The power feed was run straight from the "line" side of the dashboard fuseblock! No fuse, no circuit breaker, just a live hot wire under the seat that could have grounded out agaisnt the floor boards, seat frame, anything. When it did finally do that, it fried a big chunk of the carpet and overheated the feed wire to that section of the fuseblock. In short, if there are wiring "discrepancies" from the P.O. still in place inside the truck, get 'em out! Many people fancy themselves perfectly capable when dealing with electrical issues and things end up worse instead of better. I'd bet something that the P.O. mangled is the culprit.

 

Thanks to those who replied, but I was hoping someone made have had something similiar with regards to how it would run, with the guages pegged and whatnot.

I've been thinking about the wiring under the dash, and I'm hoping someone with a similiar set-up could check something out for me. Under my dash, there is a very small switch with two wires running to it, and it's not attached to anything, it just hangs there. Now, this is not the cut off switch, or whatever it's called, mounted to the firewall behind the brake, I know what, and where, that is, it's not that. This is a second switch that just hangs there. Now, I believe that my buddy hit that switch when it ran the first time. I thought I remember messing with it when I was first trying to diagnosis it, but I haven't given it much thought since. My new theory, is if no one else has something like this, perhaps this is a kill switch that a P.O. put in do to exactly what I am talking about, sending power to ground. It has come loose from it's mounting position, and between swinging around under the dash, and my feet under there, has been hit a couple of times. That would be a great explanation for all my problems. If someone could check, or knows first hand, that would be a big help for me.

Thanks for any help.

 

I aint like 100% sure but I dont think there should be a switch like that under the dash.......it dont sound factory to me.

What does this switch do? Can you snap a pic of it?

 

I'll see what I can do, I don't have a digital camera, but I have a disposable I'll try to use and get put on a disk. I also found a wire that was grounded to a bolt on the firewall at some point, and has broken lose, I am also wondering if the end the broke lose, at some point (and I won't discount my own doing) got wired in to a hot wire thinking that's where it belonged.

Anywho, still looking for anyone who has experiences the guage pegging stuff, and I'll see what I can do to get some pics on A.S.A.P.

Thanks!

 

Update:

Sorry, it was a while since it first happened and some of the things I found keep popping in my head, I figured I would add it incase it would help.

The alterntor case had power going to it, I could litterally use a test light on the negative post and the alterntor casing and it would light up. It would also arc a little when I would put it in for what I assume is the power in the case contacting the ground of the mounts. I had the alternator as well as the battery checked and they were both good.

 

I have an 88 that is stock. Let me know if I can help. We could always compare.

1988 EB Bronco - 302 - AOD - 3.55 Lim Slip 8.8- Manual Hubs and Transfer Case - BFG 32/11.5 AT - 209,000 miles

 

The updates just keep on coming:

Okay everyone, I checked out the extra switch, goes to a "My Valet." Looks like someone wired in a keyless entry system, I always assumed it was factory. Anyways, I don't think that has anything to do with it, as I disconnected it completely and had same problems. It almost seems like something is overheating, electrically, slowly, once it builds to a point, one demand of juice (i.e. window switch, brake, etc) the guages peg and the engine dies. I tried pulling codes, but it wouldn't work for me, so I started it, which I believe resets the computer and it has stopped dieing, though the oil pressure guage goes hard right (with or without the wire on the sending unit) and sometimes the temp guage doesn't read (I have an aftermarket electrical that is reading). Also, most of the time, when I turn the key to the off position, the oil pressure and temp both peg out all the way to the right, I can't remember if that's what it did before all the problems, so jem270, that maybe some way you can help me, if yours does that or not.

Anywho, if you are still reading this, I'm going to tinker with it this weekend, I need to get the alternator checked as it's only showing the battery is getting 11.80ish volts and is reading real low on the factory guage, like one line low.

I'll keep them coming! Thanks for everyone trying to help!

 

I'll try to look at mine in the morning. I don't drive it much. I will look at the gauges when I turn it on with out cranking it.

First thing I would do is to fix the problem with the low volts. Get a volt meter and check the pre cranking volts and compare them to the volts while the engine is running. Battery should be 12+ volts before cranking and 13-14 when idling about 1500 rpm. Some auto parts stores will test your system for free.

1988 EB Bronco - 302 - AOD - 3.55 Lim Slip 8.8- Manual Hubs and Transfer Case - BFG 32/11.5 AT - 209,000 miles

 

Thanks everyone for their replys, I appreciate everyone trying to pinpoint this one, I'm going to shed some, but not all, the light on the situation, and some of ya'll were close.

Okay, I chased stuff around, and around, following cable after cable, and when I was checking a free ground wire I found (bolted to the firewall, engine side, right above the ignition coil, has no home if anyone has any ideas, it's a thick one and the end looks like it goes into a connector of sorts) I noticed that I was getting some funny readings from that wire to the block. As it turns out, the body had 1.7 volts running through it, the block had none. So, I hooked up an extra battery cable I had and ran it from the ground post to the body and now there is only .07 volts running and my gauges stopped pegging out. It started making sense why, when I turned the key off, the gauges would peg, as they were still getting current through the body. I am guessing (no expert here) that somehow, with enough voltage running through the body, it would go through the ground in the starter solenoid and kick it over, it's the only thing I can figure.

Anyways, the truck is acting like it's suppose to, though this doesn't tell me where my body is getting the power from. I messed with the wires under the dash A LOT, sometimes it generated a resoponse in the gauges, sometimes not. I ran aftermarket gauges through the firewall, but I used grommets. I'll keep checking, but atleast for now, that extra ground has helped out a great deal!

Thanks everyone!