Electrical Problem After Shipping Bronco

[uplander]

Shipped my rig to new state. When it arrived, one headlight was so dim it looked nearly off. Next time I tried to start it there was no electrical whatsoever. Later I tried again and it started right up--one bright headlight, one dim. Next time, all dead again. Still totally dead--no lights, no crank. Battery fully charged. All parts are new in this resto. Where should I start hunting? Thanks!

 

[66ranger]

Bad ground. Start checking at battery, then ground on engine. Look at engine to body next. Headlight ground may be a separate issue.

 

[uplander]

Checked every ground I could find. All good grounds. It is a 67 U13 that is two years out from a frame off resto. All new wiring harness etc. Not an issue for two years until I shipped it. When I turned on the headlights as I was picking it up, one was very dim. Then when I got home (after driving only a couple miles) and turned key to off it was completely without any power. Battery neg terminal has one ground to engine block--clean connection.

 

[73azbronco]

Do you have a negative to frame connection? Negative to body connection? How many ohms between negative battery terminal and negative wire off of dim light?

 

[DirtDonk]

Yes, from the factory broncos had an additional ground connection to the body on the inner portion of the wheel well. That was enough when they were new, but as they get older they can use additional ones to those two. But it sounds like you only have one, which is typical of a rewire.

A good body ground will not usually totally kill the power. When it does this for you, does anything work at all? If not, then it could be one of the two main battery cables as well.

Do you know what brand of harness the wires were replaced with? If you're not sure looking at the fuse panel could tell us.

 

[uplander]

Do you have a negative to frame connection? Negative to body connection? How many ohms between negative battery terminal and negative wire off of dim light?

No negative to frame or body connection--just to block. Zero Ohms between negative battery post and negative wire in lamp plug.

 

[Rustytruck]

every time I dealt with poor headlight function it was down in the dimmer light switch and its connections. I am with everyone else in checking grounds its free and the most likely failure point without actual component failure. there are grounds at the headlight bulb connectors too.

 

[gnpenning]

Sounds like you are lacking some grounds. No matter what you should add them, might save you down the road.

The dim headlight is most likely back feeding through the filament to the headlight ground on the other side. Run a temp ground wire from the dim side to the battery ground.

 

[73azbronco]

stock headlight bulbs and buckets, as in original? Might try sanding contacts inside bulb socket.

 

[DirtDonk]

Even though the two issues might be unrelated, the bad ground thing might indicate that it's a bad battery cable on the negative side.
Would not be the first time someone encountered a bad cable even if they look good, or even new.

For that "new" part, the only time it happened to me personally the positive battery cable was less than three years old and looked brand new. Failed internally and all power would die as soon as I'd turn the key to START. Everything worked fine up to that point, but after that literally everything was dead.

If truly everything is dead, then there are only three (ok four) things that can cause this:

1. Bad positive battery cable.
2. Bad negative battery cable.
3. Blown or just a failing fusible link (it's at the end of the Black wire on the battery side of the starter relay/solenoid, powers the entire truck and charges the battery.
4. The main connector behind the ammeter in the instrument cluster. If it's rusty, loose or partially disconnected it can kill power to literally 99% of the truck.

Good luck.

Paul

 

[uplander]

Mystery solved. Headlight is bad but had nothing to do with the loss of power. I disconnected the harness from where it plugs into the firewall. Then reconnected it. Then cleaned out the original fuse box. Back in business.