3G Alternator Upgrade with Centech

[Fitz24]

Installed a centech wiring harness 10 years ago when I built the EB. Had original alternator with external regulator. Alternator worked as it should until I installed AC, a pusher fan, and HID headlights. Stock alternator can't keep the battery charged when running AC and pusher fan.

Upgraded to a 130a 3G to handle the extra loads and winch. Doesn't seem to be charging properly. Never shows a voltage over 12.5 and drops when I turn on lights, AC, etc. I think my mistake is connecting the large yellow Alternator wire and the large red Bat wire in the Centech harness to the Bat+ of starter solenoid . I have a #6 from 3G to Battery terminal.

Anyone have similar issue and find the cause?

Thanks

 

[DirtDonk]

With the 6ga cable doing the charging duties, you no longer need the Yellow wire.
I don't think it's hurting anything, and likely is not causing your trouble, but I wanted to make that clear that the new cable is doing all the work.

Did you connect keyed power from one of the Centech's green wires to the Green w/red wire coming out of the 3-wire plug on the side of the alternator?
And did you connect the Yellow w/white wire from the same plug directly to the alternator's BAT terminal in addition to the large cable? Or it could go anywhere the battery has a positive terminal. Either to the battery, to the starter relay, or to the alternator itself. They're essentially the same thing.
The factory puts it closer to the battery, but most installations simply run it over to the 6ga cable and the BAT post.

And finally, most 3G's need the White w/black wire plugged into the single STA terminal on the side of the alternator. If yours is, try disconnecting it and checking voltage again. I've had at least two 3G's that would only work with the STA wire disconnected.

Start there and see what you get.
And if you feel like it, post up some pics as well.

Paul

 

[Fitz24]

With the 6ga cable doing the charging duties, you no longer need the Yellow wire.
I don't think it's hurting anything, and likely is not causing your trouble, but I wanted to make that clear that the new cable is doing all the work.

Did you connect keyed power from one of the Centech's green wires to the Green w/red wire coming out of the 3-wire plug on the side of the alternator?
And did you connect the Yellow w/white wire from the same plug directly to the alternator's BAT terminal in addition to the large cable? Or it could go anywhere the battery has a positive terminal. Either to the battery, to the starter relay, or to the alternator itself. They're essentially the same thing.
The factory puts it closer to the battery, but most installations simply run it over to the 6ga cable and the BAT post.

And finally, most 3G's need the White w/black wire plugged into the single STA terminal on the side of the alternator. If yours is, try disconnecting it and checking voltage again. I've had at least two 3G's that would only work with the STA wire disconnected.

Start there and see what you get.
And if you feel like it, post up some pics as well.

Paul

I have everything hooked up as you described. One thing I noted tonight is that my keyed power on the green line is only 10.5 to 11 volts while battery is showing 12.5 volts. Not sure why and wondering if that is not enough to do the job it is supposed to. I'll get some pictures as soon as I reinstall the 3G. I pulled to have it tested. Tested good.

 

[DirtDonk]

Well, I don't like to see that much voltage drop on a circuit like that, but I don't believe it's low enough to cause the alternator to not work. But I really don't "know" so that's all just assumptioning at this point.
Best to find out why.

But that should be easy enough. It's a direct shot between the ignition switch and the alternator if you used the wire intended for that.
The factory does it that way for sure, and I believe that Centech does as well. But they supply so many extra Green wires for accessories I'm not sure.
Did you use the one they had originally over on the passenger side listed for the alternator regulator?

When they test it did you watch them? If so, did they connect the stator wire (White w/black) to the side of the alternator?

Paul

 

[Fitz24]

Well, I don't like to see that much voltage drop on a circuit like that, but I don't believe it's low enough to cause the alternator to not work. But I really don't "know" so that's all just assumptioning at this point.
Best to find out why.

But that should be easy enough. It's a direct shot between the ignition switch and the alternator if you used the wire intended for that.
The factory does it that way for sure, and I believe that Centech does as well. But they supply so many extra Green wires for accessories I'm not sure.
Did you use the one they had originally over on the passenger side listed for the alternator regulator?

When they test it did you watch them? If so, did they connect the stator wire (White w/black) to the side of the alternator?

Paul

Did use the centech green wire that ran to the original regulator. I'm going to find the other end (hopefully at the ignition switch) and check voltage there.

They tested the alternator behind the bench, so no, didn't see if they hooked up the stator wire. I'll try leaving disconnected once I get the alternator installed tonight and see if that helps.

Thanks for all your input. I'm gettting a little frustrated and it's always good to see if others experienced the same and found a resolution. Sometimes you tend to forget the basics and forget to check the most common causes.

 

[DirtDonk]

If that wire has a splice in it to extend it to the new alternator, it could be that the splice is not perfect and there is a loss there.
Or the switch could be faulty.
Or too, you could do your best impression of a pretzel(!) and crawl under the dash to peek at the back of the fuse panel to make sure that the three large nuts are not loose.
I've never personally had that happen, but there was one installation a few years ago where one of the nuts came loose (no way to know what the owner or the PO had done though, so can't blame Centech out of hand) and caused some big resistance and heat buildup.

Worth a shot anyway, if you don't find anything else obvious.
But that aside, you can run a temporary jumper wire directly from the battery to the Green wire on the alternator to see if that changes anything. If not, then you know that, low voltage or not, this is not the issue.

But an alternator that tests as good on the bench can really only have three issues on the truck.
1. Yellow sensing wire not connected properly.
2. Green exciter wire not connected properly (or getting enough voltage?)
3. Belt so loose it's slipping and not letting the alternator charge.
(edit 4. Poor grounding through the case?

The belt can slip on these things without squealing or other clues, so don't go by sound alone. Verify.

I think those are the main possibilities. Can't think of any others at the moment. The engine should have a good ground or your starter won't work.
Hmmm, grounding... Is the alternator bolted to a freshly painted head by any chance? Bolt hole a little rusty by any chance too? Do you have a separate ground wire from the case to the body/engine/battery?
Not grounding well enough could cause trouble too. I'll go back and add it to the list...

Paul

 

[Fitz24]

If that wire has a splice in it to extend it to the new alternator, it could be that the splice is not perfect and there is a loss there.
Or the switch could be faulty.
Or too, you could do your best impression of a pretzel(!) and crawl under the dash to peek at the back of the fuse panel to make sure that the three large nuts are not loose.
I've never personally had that happen, but there was one installation a few years ago where one of the nuts came loose (no way to know what the owner or the PO had done though, so can't blame Centech out of hand) and caused some big resistance and heat buildup.

Worth a shot anyway, if you don't find anything else obvious.
But that aside, you can run a temporary jumper wire directly from the battery to the Green wire on the alternator to see if that changes anything. If not, then you know that, low voltage or not, this is not the issue.

But an alternator that tests as good on the bench can really only have three issues on the truck.
1. Yellow sensing wire not connected properly.
2. Green exciter wire not connected properly (or getting enough voltage?)
3. Belt so loose it's slipping and not letting the alternator charge.
(edit 4. Poor grounding through the case?

The belt can slip on these things without squealing or other clues, so don't go by sound alone. Verify.

I think those are the main possibilities. Can't think of any others at the moment. The engine should have a good ground or your starter won't work.
Hmmm, grounding... Is the alternator bolted to a freshly painted head by any chance? Bolt hole a little rusty by any chance too? Do you have a separate ground wire from the case to the body/engine/battery?
Not grounding well enough could cause trouble too. I'll go back and add it to the list...

Paul

Thanks for all the input Paul. I reinstalled the alternator last night so all mounting surfaces are cleaned. I do not have a separate case ground so may add one so I know grounding is not an issue.

I checked voltage at the fuse block for the ignition and Alt fuses. Both had 10.8 volts with key on, 0 with key off. All other fuses had same voltage as battery.

One more thing to note, when I turn key switch on, battery voltage drops from 12.3 to 11.4. Radio, electric fuel pump, and PCM running (have Howell TBI).

I'll check those things you listed tonight and see if I find anything. I will also reconnect all wires to alternator and crank it up to see if anything has changed. If not, going to need to charge battery again

 

[DirtDonk]

Interesting voltage readings. But you're zeroing in at least. You know the loss is not under the hood, but prior to, or at the fuse panel. Sounds more and more like the ignition switch connection or the switch itself.
Both at least are easy enough to check. Assuming you're still young and flexible enough to get under the dash with a meter that is!

The battery voltage dropping like that when you turn the key on is "kind of" normal. They will often do that, but yours does seem a bit more than you'd expect short of cranking the starter. Instant readings will often drop to 10.5 or so during cranking, but dropping a full volt just by turning the key on deserves a bit more quality time with your brainpower and meter.
With the pump and such, it might be normal. I'll see if I can remember to check mine tomorrow to see if it's similar.

Oh, and our cable is 30-strand.

Paul

 

[Fitz24]

Well, put it all back together and wired back up tonight. Started it up and what do you know, 14.5 volts at the battery!! I can only assume somewhere in the wiring there was a bad connection. Enough to drive a person crazy but glad to see it working properly.

Thanks for all you time and input Paul.

 

[DirtDonk]

Congrats! Well at least for now anyway;D
Hopefully it stays that way. Maybe it was just moving things around that did it, or something. With luck it'll be more than just temporarily fixing itself.

I'm still waiting for the other shoe to drop on mine. Had a very large fuel leak out of the return line one day. The next day it's tight as a drum.
Obviously it's waiting for me to be as far from home as possible before leaking again!

Glad yours is pumpin' out the juice.

Paul