Battery drain when i connect the voltage regulator

[JohnJohn]

I have been trying to track down a major battery drain on my trail rig for a while now. The battery is new and tested I also have a new centech harness in the truck.

When I hook the voltage regulator BT yellow wire up to the positive side of the starter solenoid it pulls 26 amps. I even put a volt meter on the battery and when I hook up the voltage regulator up I can watch the voltage start to drop. If I let it sit there it will suck the battery dry in an hour or two.
I put a new regulator on but still had the problem. I even disconnected the big alt wire from the back of the alternator but it still pulled amps.
Any ideas?

 

[JohnJohn]

I just noticed the PO installed a BC Bronco 3G alternator. Do I still run the external volt regulator with a 3G?

 

[DirtDonk]

No.

Paul

 

[DirtDonk]

Ok, now that that's out of the way, get rid of the regulator all-together and cap off all the wires connected to it.
Since the yellow wire is separate it sounds like, just get rid of it.

"Internally regulated" is just that. So dual regulators is not correct ever, unless you have to trail-rig something to get you home with a dead internal one. But I'm not even sure that would work.

So are you still using the Centech's large Yellow wire as your charge wire, or does your alternator have a heavy gauge wire straight from the alternator's output stud to the battery or starter relay post?

Paul

 

[JohnJohn]

Thanks so much Paul.
The PO ran the stock centec yellow alt wire from the alternator through the firewall. Should I disconnect it and run a heavy gauge wire directly from the alternator to the starter solenoid?

 

[DirtDonk]

Unfortunately, yes.
With a 90 amp 3G, it's possible to work it, but you might not always be lucky. With a 130+ amp 3G however, you're just living on borrowed time.

You lose the function of the ammeter unfortunately (most people are happy to be rid of it, but not me), but with that much current possible from the alternator, it's best to run a wire straight to the battery and either leave the big Yellow wire where it is for safe keeping, or better yet, "re-purpose" it somewhere else as a great and powerful Oz power source for other accessories. It's big enough to handle a nice sized auxiliary fuse panel or power buss if you want.
That's what I do with them.

Reason I prefer that method over leaving it in place, is that while it's perfectly safe most of the time, if your large wire ever fails on you while it's really charging heavily, your Yellow wire might not be big enough to handle it.
If you never plan on winching, or letting your battery go completely dead, then you've got less to worry about. I'm just a worrier that way.

So that's just a long way of saying, it's your choice, and certainly works for some people, but there are good reasons to not use the Yellow wire anymore.

Paul

 

[DirtDonk]

Oh, and the normally recommended replacement charge wire size is 4 gauge. While I usually use the smaller 6ga for easier routing (it's still plenty of overkill), and even have a supply of 8ga because it's also plenty for most applications, bigger is better (as in, safer) so if there is room, go big.

Heck, for the short distance between the battery and alternator on a Bronco, if you wanted to you could probably use 10ga for awhile. But it would be borderline and too much possibility of melting down in the future. So consider 8ga a minimum, and 4ga an optimum.

I just ran one with 6ga back over the engine, behind the wheelwell, up along the side inner fender with a Mega-Fuse holder, and then to the starter relay.
Should be hunky dory for the long haul.

Paul

 

[JohnJohn]

Paul
I owe you a few beers. I just went out and removed the yellow BT wire and the regulator then installed a 4 gauge wire I had and started the truck up. Everything looks great so far. It runs fine and holds a bit over 12v at the battery.
I can't wait to see where she is in the morning with it hooked up all night.
Hope you can make it to an MEB RoundUp soon so I can meet you some day.
Thanks
John

 

[DirtDonk]

Look forward to it John! Don't get out much these days, but will work it out someday I'm sure.

Once it's been running, and has been revved up and run a bit, you should really want to see about 14.5 at the battery (while it's running).
Just over 12 may be temporary, but if it lasts then you still have an issue to deal with. Should only read that way when the engine is off.

But at least you may not have the drain! At least we hope not.
What are the other connections at the alternator? You should have 3 or 4 wires normally from a 3G connector. If you don't use the White w/black wire for your carb's choke (or if it's not present), then you should still have the Yellow wire attached straight from the plug to the main output post of the alternator, or, straight to the battery. This is the battery charge sensing wire.
There should also be a Green, or Green w/yellow wire that's gets power with the key ON.
Check that there is 12v to the Green wire with the key ON, and make sure there's a good connection to the Yellow wire.
If it's all good, then you may just have a bad alternator or internal regulator.

Good luck. Hope it's just a loose connection or slow-starting alternator.

Paul

 

[JohnJohn]

Paul
I went out this morning and hooked two of the old voltage wires together. I hooked the REG S green wire to the FLD wire that runs to the alternator. Not only did the truck start this morning after being hooked up all night but it was also pumping out 14.4 volts.
Thanks again.
I am sure this is not the end of my previous owner discovery but at least he bought lots of good stuff. It was just his implementation of the stuff that came up a bit short.

 

[DirtDonk]

You sure it was a "field" wire on the alt? What color is it, and does it come straight out of the plastic connector, or directly off of some stud on the back of the alternator case?
Your output is perfect, so that's good. I just want to make everything is going where it's supposed to.

Paul

 

[JohnJohn]

thanks Paul.
I will double check but one of the wires off of the alternator plastic connector is now running to the RegS wire to get a key on 12v source.