I'm having some sort of electrical problem on my 1975 Ford F-150 and am hoping folks on here can help. The problem I'm having is it won't start, like the battery is dead but when I pop the hood I discover the battery cables are split and black like they caught on fire. The battery tests good, so I buy new cables and drive for awhile and then same thing will happen. It used to happen every 4-5 months but over the last year it has been happening more frequently, until this last time and now replacing the battery cables doesn't get it started again. It acts like the battery is dead, even though the battery continues to test good. The key turns and nothing at all happens.

Some folks have guessed it's the ground, but the ground is connected to the engine block. Which is correct I think but perhaps I don't have it connected to the best place on the block? When I bought the truck I took it for a tune up and the mechanics connected the ground to the truck's frame and over the next week my battery died. That's how I learned it had to be connected to the block.

I have replaced the ignition switch, the lock cylinder, the battery cables, the selenoid. The only thing left I can think of is the wiring between the ignition switch and the battery is messed up, causing the battery cables to pop and catch on fire a little. I didn't grow up working on trucks, am learning as I go along with this one that used to be my daily driver, and I hope to get it back there sooner than later. My experience with mechanics for old trucks in my area has been discouraging - some tell me I have the wrong carburetor on because they think it's a different engine (I don't have the wrong carburetor on - I might not be an expert at cars but I'm not an idiot otherwise) - so I cannot bring myself to take it somewhere for fear of them messing it up or charging me an arm and a leg as they hunt for the problem in the wiring. I feel like the problem might be simple and I'm just not educated enough to figure it out. Hoping folks with lots of old truck experience may be able to give me some clues to getting my truck running again.

Thanks in advance for your help.

 

The battery cables are physically split apart? The amount of current required to make that happen is gargantuan. Is it just the positive cable, or both? Or is it the starter cable? Can you describe how the battery cables are routed?

 

Thanks for the reply. The first time this happened yes it actually split them apart about an inch - those battery cables were on the truck when I bought it and they were all white with a connection to the block that was bigger than cables have now, so I am assuming they were old. I can't say for sure if every time it splits them, this has happened 4-5 times over a year or so, but it definitely did the first time and all other times it at least turns them black indicating fire has happened. That first time it was the negative that split - pretty sure since then it's both that char.

I'm not home right now so I can't look at it but tonight I'll look and repost exactly how things are routed. Maybe post a pic or two. Thanks!

 

Hello, and welcome. There's a few electrical wizards roaming here so hang tough...they'll be along and you'll get it fixed.

360 or 390 FE motor? Points distributor? A/T or M/T? Some basic motor and running gear info would help narrow a few problems down.

You are correct on the grounding ideas...the more, the better, within reason. I would have a good ground from the neg batt to the block, from the neg batt to the immediate frame/fender, and another from the back of the block to the firewall. All clean and secure, of course.

The solenoid and regulator should be grounded also - clean and secure.

A little troubleshooting now ... Just a quick test now for your charging system....When running, what battery voltage do you have? 14.5 VDC and steady is good. Jumping around or steady higher is not good.

Check the wiring from the batt to solenoid to regulator to the alternator for brittle insulation and clean, good connections...check your distributor electrical wires/connections and ICM for good connections.

Wires getting hot usually means lousy/unsecured ground connections. Check and fix those first.

 

Thanks, Filthy Beast. Great info on the grounds. When home tonight I will check out all the current routing and see what I can improve. Will post info on current setup and any improvements, won't have time to do improvements until weekend.

Answers to your questions: it has a 360, A/T, will have to check on points distributor. Regarding battery voltage, I can't get it running so can't check yet.

I'm sure this will be a silly question, but here:
I would have a good ground from the neg batt to the block, from the neg batt to the immediate frame/fender, and another from the back of the block to the firewall.
do you mean there will be more than one ground coming off neg batt to these different locations? I didn't know you could / should do multiples.

I'll be back with follow up info soon and this weekend will work on grounding the **** outta this sucker. Thank you!

 

I would have a good ground from the neg batt to the block, from the neg batt to the immediate frame/fender, and another from the back of the block to the firewall.
do you mean there will be more than one ground coming off neg batt to these different locations? I didn't know you could / should do multiples.

Absolutely you should have redundancy/multiples on ground connections! Ok, let me specify a bit on the batt ground....one heavy gauge from the batt neg to a good, clean engine block connection. Those newer cables have a spot attached for another connection, by the batt neg terminal hookup, yes? Hook up an 8 gauge wire to that neg cable and then to the immediate fender area next to the battery. From the back of the motor, there should be a spot on the intake or head to hookup a ground strap from the block to the immediate firewall area. If not, make one!

There are more grounds to be had/made but these should suffice for the motor.

By the way, fmc400 is The Man when it comes to this electrical stuff...follow his advice and you'll be gold!

 

Awesome information, so excited to work on it this weekend. Will post results. Thanks so much.