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Battery and alternator wiring

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centexk5

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I'm getting ready to redo my battery and alternator wiring and want to make sure I get it right. Going to upgrade to 1/0.

Currently the battery has a 4ga negative going to a bolt on the exhaust manifold and that's it for grounding. Nothing from the engine to frame. I'm assuming the alternator is grounded from being bolted to the engine. I've searched and can't find a single ground wire from the engine to the frame or the body to the frame so I'll be adding those.

For the positive side, the battery has a 4ga wire running to a post on the starter. The alternator has a plug with 2 wires coming out of it that are maybe 12ga that go to the same post on the starter. This is where I need the help on wiring and it's probably because I'm over thinking it. How should the positive cables be ran? I'm attaching a couple of pictures of the alternator and the starter where the wires go.

IMG_20200119_150939.jpg

IMG_20200119_152517.jpg
 
I don't remember what year yours is, but the power feed for the fuse panel usually comes from the post on the starter. And the charge wire from the alternator can go to the starter or to a junction block on the firewall. It is possible to move those both to the battery terminal, but it needs to be done in a way to not make a disaster at the battery with lots of connections that can get corroded. And extending the wires should be done with some circuit protection as well as abrasion protection. I also like to use a larger wire size to help minimize voltage drops.
I also upgrade the ground wires above the factory ones.
 
I personally wouldn't worry about a charge wire larger than 8 gauge, it is easier to route that, and it will carry plenty of amperage. Your 12 SI alternator is probably only putting out 100 amps unless it's been worked on.
And multiple ground wires don't have to be dramatically oversized, I used my old 4 gauge cables for them. Saved money on cable and terminals that way.
 
The cable is cheap for me and I've got the tools to crimp it so figure it can't hurt.
 
6872xtc said:
I personally wouldn't worry about a charge wire larger than 8 gauge, it is easier to route that, and it will carry plenty of amperage. Your 12 SI alternator is probably only putting out 100 amps unless it's been worked on.
And multiple ground wires don't have to be dramatically oversized, I used my old 4 gauge cables for them. Saved money on cable and terminals that way.
Click to expand...
Yeah I keep the grounds short and original 4 gauge.
The positive is the one that gets long and needs to get upsized.
I went with 1/0 on mine as well.
I have a bout 5 grounds so I am good with 4 gauge
 
For grounds I was thinking battery to frame, engine to frame, and body to frame in a couple of spots and call it good. Longest would be the battery to frame but that should be 18" so not much at all.

I've also debated doing a grounding bus bar on the firewall and one inside the cab as well. Did one on my dad's bronco but it was a fiberglass body so slightly different situation.
 
I was taught and have always seen the main ground cable should got to the engine. The starter is typically the highest amp draw to get the engine turning, especially. Just a thought, otherwise it sounds like a good plan!
 
As an aside, I see ~14v across the system (fuse panel, wiper motor, battery) on mine with a stock wiring setup, albeit with a cs130 alternator. That's with everything on...high beams, heater, wipers, etc.

Outside of running some serious draw equipment (huge sound system, winch?) the starter is by far going to be the largest draw. And that's easily rectified with a gear reduction design.

Off the top of my head the setup on mine has a 4ga ground from battery to engine block, and a maybe 12ga wire off the 4ga wire to the core support and to the frame. Braided copper strap from back of passenger side head to firewall. My battery ground is right to the alternator bracket.

IMO, good connections, using quality components, are the key. Electrical problems normally relate to loose or broken connections, and corrosion. I always make sure to use dielectric grease on any connection I'm making, even the sealed connectors. And I've done away with splicing so as to keep the wires as shielded as possible from corrosion.
 
dyeager535 said:
As an aside, I see ~14v across the system (fuse panel, wiper motor, battery) on mine with a stock wiring setup, albeit with a cs130 alternator. That's with everything on...high beams, heater, wipers, etc.

Outside of running some serious draw equipment (huge sound system, winch?) the starter is by far going to be the largest draw. And that's easily rectified with a gear reduction design.

Off the top of my head the setup on mine has a 4ga ground from battery to engine block, and a maybe 12ga wire off the 4ga wire to the core support and to the frame. Braided copper strap from back of passenger side head to firewall. My battery ground is right to the alternator bracket.

IMO, good connections, using quality components, are the key. Electrical problems normally relate to loose or broken connections, and corrosion. I always make sure to use dielectric grease on any connection I'm making, even the sealed connectors. And I've done away with splicing so as to keep the wires as shielded as possible from corrosion.
Click to expand...

Don’t forget that electric windows draw a bit of current too, albeit for short bursts. I usually roll them both up together after I park which would be about a 25-30 amp draw (15 per window). I forget how much the rear window draws.
 
And on the windows, side or rear, if the mechanisms arent in good shape, the motors will draw a bunch more, and perform worse doing so, than if they are lubed up, tracks are in good shape, adjusted properly, etc.

From the factory, I dont believe these trucks were wired inadequately. As they age and we add electrical draw, we begin to tax the existing system, and the problems we see are more to do with age and condition vs. an initially cheaply made system (even though GM did it as cheaply as they could). I STILL haven't replaced the factory copper clad aluminum ground cable in mine. Even though its severed a couple of strands, it still does the job. Needs replaced at some point, but getting the truck on the road is more important to me at this time, than a future, potential issue.
 
I've got a 12k winch, lights, and a stereo amp. And the alternator is just an oreilly's special I got to get the truck running so it's probably at best 65a.
 
If you are running one of the 63A alternators, and electrical is one of your concerns, I'd at least consider stepping up to the cs130, if not the cs144.

Better, specifically more output at idle, not to mention the overall max output. Will work the CS series less with the same load, but better able to cope with higher loads to boot.
 
I understand this. It's not happening right now. $40 in cable is easier to deal with than a $100+ alternator and the bigger cable will work with the larger alternator.
 
The factory grounded the battery negative right to the alternator bracket,and the engine had 2 braided ground straps from the rear valve cover bolts to the firewall--some trucks also had a braided ground cable from the transmission case to the frame..
The exhaust manifold bolt is a bad choice for a ground,the heat will increase resistance...

What I've done on my GM trucks was to take off the thick red wire at the starter solenoid that goes behind the positive battery cable (some trucks had 2 red wires,and both types should have fusible links in them,close to the starter)..those wires were run thru a steel conduit tube bolted to a bell housing bolt,and they often got roasted inside it,and would short to ground,or the fusible links would melt..

Older trucks before 1973 had those wires (that feed the rest of the cab & truck) connected right to the battery positive post,or a junction block near it,I decided to copy that arrangement after having two trucks melt those wires inside the conduit--I had to cut & extend them about a foot to do so,I left the fusible links intact to provide protection--never had any issues since then..this also makes it easier to replace a starter,now you'll only have the positive battery cable and the thick purple wire that activates the solenoid to crank the engine to deal with at the solenoid..

Usually the rest of the alternator wiring back to the fuse box remains good unless one gets pinched or melted and shorts out--one wire that goes to the #2 terminal on the 2 wire alternator plug sometimes gets a bad connection at the fuse box,or it decides to turn to powder somewhere along its run--if that wire doesn't send 12V to the alternator with the key "on",it will not charge--this sells a lot of new and rebuilt alternators ,when they had nothing wrong with them..

It wont hurt to run an 8 gauge wire from the alternator "main output stud" to the positive battery terminal,it'll help make up for any voltage loss from old wiring being corroded or have other defects somewhere along its run..
 
That's exactly how mine is done with the two wires through the conduit.

And there are no other ground wires on this truck that I can find beyond the one from the battery to the exhaust manifold. Which is part of the reason I'm doing this project.

So what you are saying is remove those 2 wires from the starter solenoid and then route those to a junction box for the power for the rest of the vehicle? Or in other words, instead of the starter solenoid being the junction box for the trucks fuse block, move the wires and make an actual junction box for it.
 
Yes--I run them right to the positive battery terminal...you could add a junction block close to the battery,if you don't want multiple wires on the battery terminal..
 
diesel4me said:
The factory grounded the battery negative right to the alternator bracket,and the engine had 2 braided ground straps from the rear valve cover bolts to the firewall--some trucks also had a braided ground cable from the transmission case to the frame..
The exhaust manifold bolt is a bad choice for a ground,the heat will increase resistance...

What I've done on my GM trucks was to take off the thick red wire at the starter solenoid that goes behind the positive battery cable (some trucks had 2 red wires,and both types should have fusible links in them,close to the starter)..those wires were run thru a steel conduit tube bolted to a bell housing bolt,and they often got roasted inside it,and would short to ground,or the fusible links would melt..

Older trucks before 1973 had those wires (that feed the rest of the cab & truck) connected right to the battery positive post,or a junction block near it,I decided to copy that arrangement after having two trucks melt those wires inside the conduit--I had to cut & extend them about a foot to do so,I left the fusible links intact to provide protection--never had any issues since then..this also makes it easier to replace a starter,now you'll only have the positive battery cable and the thick purple wire that activates the solenoid to crank the engine to deal with at the solenoid..

Usually the rest of the alternator wiring back to the fuse box remains good unless one gets pinched or melted and shorts out--one wire that goes to the #2 terminal on the 2 wire alternator plug sometimes gets a bad connection at the fuse box,or it decides to turn to powder somewhere along its run--if that wire doesn't send 12V to the alternator with the key "on",it will not charge--this sells a lot of new and rebuilt alternators ,when they had nothing wrong with them..

It wont hurt to run an 8 gauge wire from the alternator "main output stud" to the positive battery terminal,it'll help make up for any voltage loss from old wiring being corroded or have other defects somewhere along its run..
Click to expand...
I agree on both accounts.
Alternator bracket is where I ground not the exhaust manifold. And I relocated the power wires away from the starter and on the battery
 
Always remember that you should have a fusible link or large fuse if going alt to battery direct.
 
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