Hello,

I just stumbled upon this site and I hope that you guys can help me out. Last summer I had the engine in my 1989 F-150 rebuilt. It is the 5.0 with the Electronic 4 speed transmission and 4 wheel drive.
Anyway, the mechanic did a great job, and I drove the truck from Virginia to Las Vegas, NV where I live. On the way, I hit a bump in the road...(pothole or something) and all of the sudden, the electronic door locks stopped working and so did the roof mounted cab lights, both the interior light, exterior bed light, and map lights.
Somehow, a few hundred miles later, the door locks began to work again. No such luck with the cab lights. Then suddenly, the truck began to run very very rough. Seemed like a miss, so I pulled the plugs, but to my suprise they were just like new. Around the same time, I noticed the voltmeter was wildly fluctuating and then the battery died suddenly. It was a new battery, so I replaced both the battery and the alternator, hoping that this was the problem, however, the studdering and stammering continued for a while until the truck became undriveable... so I parked it for a few months.
About 2 months ago, I decided to mess around with it again, and would you believe it... the cab lights came on and the truck ran like new for about 2 minutes until it just up and died. I started it back up, and it ran just like before, with all of the hesitation and stuttering, but again with no cab lights.
Here's where you fellas come in... has anyone had a similar problem, or do you know what is wrong with this truck. I of course have checked the fuses and the 2 circuit breakers, they are good.
Any help is helpful.

Thanks,

MooseVegas

 

Sounds like a wiring problem to me - flaky connector, pinched wire, corrosion, something like that. Those are nasty problems to track down.

 

X2, good luck

 

had an 82 f100 similar problems had a short in the wire harness inside the dash so i was told by the mechanic said it was 1 wire causing all my problems

 

Yep, it's probably just some little stupid thing like that, but finding it can be a real chore.

 

The common point to most of those circuits is the driver's kick panel, beside the e-brake pedal. The connector for the cab lights is near the floor down there; it's a 1-pin connector on a plain dark brown wire (the parking light circuit). The door locks (& windows) go thru the big connectors tucked inside the lower A-pillar. The EEC uses at least one ground down there (look for a green hex-head screw with several black wires going to ring terminals). The inertia switch COULD be on the firewall forward of the brake pedal under the column.

So I'd inspect that area carefully & thoroughly, and if you don't find anything obvious, pick one symptom & diagnose it systematically until you resolve it. Then go to the next symptom - maybe some of them will overlap & you'll find the common failure point.

 

Sounds like you have a floating ground that is causing all you electrical problems. In other words you have either a short or broken wire some where in your electrical system causing all your problems.

 

Hi Moose,

hmustang, You hit it on the head, it is a Floating Short(ground).

Ok Steve has an excellent place for you to start. I had a similar problem in my '88 F250, the main wiring harness that goes thru the firewall out to the engine compartment, had a bad grommot!!! I had an INTERMITTENT short, similar to yours, all kinds of problems. FYI it took me forever to find it, but I finally did!

The wiring harness protector was brittle cut and rotten, grommot was in place , but also was brittle and rotten. Wire was cut on the bottom side, at the metal at the firewall entrance, just enough to give me a intermittent problem. Couldn't be seen or detected from top or by feeling because the harness protector has ridges.Took for ever to find.

I would check the easy places as Steve suggests, then, all grommots where the wiring harness passes thru the truck as in the firewall, cab to doors, etc.

If you have trouble finding it with a visible inspection, get the truck in the dark, e.g. garage with the lights out, at night. Use a flashlight to locate the harness turn out the flash lite then move the harness around to simulate the pothole or driving vibration. This is how I finally found the problem, the lights were out and but I was home, with a flashlight and determination.

Good Luck & hope you find it.

Lyndon