Electrical Problem - need help!

montgomeryba · Post by **montgomeryba** » Mon Feb 17, 2014 5:58 pm

I have a 70 Bronco that has had electrical issues for a while. Died for good over a year ago, easy diagnosis was dead battery. Had to save up now added new battery today but NOTHING - no power. Before it died for good I was able to push start for a couple of months and even as the battery finally gave up I still got some low electrical flow - lights, lighter, etc. Changed the starting motor relay while it was down - could that be a source of problem? It now has zero power even with a brand new battery. I'm checking connections and trying to figure out wiring diagrams but feel like I'm beating my head on the wall. Any help is greatly appreciated!![/b]

IBROKENIT · Post by **IBROKENIT** » Mon Feb 17, 2014 7:28 pm

It took a year to save up for a battery? At that rate it's going to take another year to get a few more parts to be able to get it turning over. Make sure to save up for gas before you start it up.

Try checking connections at the starter solenoid, starter, voltage reg, ignition switch. A good EB manual is always handy to have.

69brightbluebronco · Post by **69brightbluebronco** » Mon Feb 17, 2014 8:42 pm

check your grounds.
make sure you have a good ground strap from the battery to the engine block, and from the block to the body too.
check for continuity on the battery cables? and corroded or lose connections?

start at the battery and big cables and work your way down. not a lot to go wrong in this system.

DirtDonk · Post by **DirtDonk** » Tue Feb 18, 2014 1:27 am

You got yourself a workout push-starting that heavy truck for sure!
Hmm, slowly went out instead of just dying all at once then. I'd agree with what was said about checking for rust/corrosion at all the main connections to the battery and double that for the ground connections. Frankly Ford didn't put many on an EB to begin with. Add 40 years or so to the mix, and you got yourself a recipe for not starting.

You might have had a slowly deteriorating fusible link wire at the starter relay too. That would be the large Black wire on the same stud as the Battery cable.

Same for the one bullet-connector just behind the instrument cluster and ammeter. It's the large Black wire (sometimes with a stripe) and is your main power wire for the rest of the truck. Pull the connector apart and check for clean contacts and a good tight fit.

What's the overall condition? What else has been done in the way of modifications? What alternator?
Does everything else still work when it's doing this? Lights, heater, stuff?

Oh, and another thing to check on your '70 are the two main firewall wiring connectors there behind the engine. With the battery disconnected, pull them both out and check for loose or broken wires or whatever, then put them back together. If there's some corrosion, maybe that will be enough to clean them up temporarily.

Good luck.

Paul

montgomeryba · Post by **montgomeryba** » Tue Feb 18, 2014 9:27 am

Thanks - I'm working through it systematically. The truck is in good shape but the electrical has never been upgraded or worked on - I've done a lot with the body, engine, axles and tranny but stay away from electrical - always has been my weak point. The electric mods are pretty much limited to a radio, air horn .... can't think of any other things but the wiring does look like a rat's nest. Stock alternator - haven't made the 3G upgrade yet. Do have an electric distributor with built in coil. I've been going through all my manuals and wish I had a clearer picture of how it should look. I will be going through all the suggestions - thanks, I really appreciate it!

Barry

Tom Dummer · Post by **Tom Dummer** » Tue Feb 18, 2014 2:01 pm

Use a meter on the battery, hot and ground. move the ground side of the meter to the body to see what voltage is there, check it on the frame and the firewall. Then move on to literally following the power wire to the starter and out to the other systems. Somewhere along the way you should see a drastic voltage drop at one of the connections. Drawings will show you what was there in 1970, might hinder you too much now.

DirtDonk · Post by **DirtDonk** » Tue Feb 18, 2014 7:20 pm

Rat's nests are the norm with these things. For some reason, most of the PO's must've thought they were electrical geniuses and that nobody else knew what they were needing. The end result is an explosion at a spaghetti factory!

Good luck

Paul

Tom Dummer · Post by **Tom Dummer** » Tue Feb 18, 2014 7:26 pm

I need to clarify. Once you check the grounds at different locations, put the ground lead on the battery and probe for power at different points.