Alternator with internal regulator
 

I'm assuming this alternator has an internal regulator, but it's not listed on oreilly as having one.
https://www.oreillyauto.com/detail/b...rwd?q=V111621A
It looks the same as this one that is listed as having an internal regulator. I had a new dead battery, and I just used the LMC plug to bypass the external regulator. Hoping to check the basics before looking for loose ground wires and drains. Battery died in about two days.

https://www.oreillyauto.com/detail/u...kup-rwd?q=Alte

Re: Alternator with internal regulator
 

Yes, the alternator in the O'Reilly link appears to be an internally regulated Delco 10SI.

If it's charging okay but draining the battery when the engine isn't running, check to make sure the 2 wires that plug into the alternator aren't accidentally swapped. If you unplug the connector and measure the voltage on the two wires, the wire that goes to terminal #1 should only have power with the key on while the wire going to terminal #2 should be live all the time. The terminal identification markings (#1 & #2) should be cast into the alternator case.

Re: Alternator with internal regulator
 

Thanks ray
Will do

Re: Alternator with internal regulator
 

I figured a picture is worth a thousand words.

#1 seems to be drawing 8.5 volts constant after 10 minutes of sitting with the key off(????) (white wire from external regulator)
#2 seems to be drawing 11.9 volts constant (blue wire from external regulator)
the other red wire is also 11.9 volts constant (red wire from external regulator.

Re: Alternator with internal regulator
 

The 11.9 V readings on both the #2 and BAT stud red wire are okay. Although they should be up closer to 12.6 V for a fully charged battery.

The 8.5 V reading on the wire going to the #1 terminal is a concern though. That was measured on the white wire with the connector unplugged from the alternator, correct?

Could you also post a pic showing how the wires are connected where the old external regulator used to be?

Re: Alternator with internal regulator
 

The readings were taken from the harness while connected to the alternator, both at the alternator, and where the wires go into the LMC external regulator adapter plug.

When I pulled the white alternator plug I got 0 volts on both wires.

Re: Alternator with internal regulator
 

You should forget the external regulator plug and run the red wire from it directly to the no,2 on the alternator and run the brown wire next to it directly to the no. 1 terminal on the alternator.

If you unplug the alternator plug and measure the volts on the white wire (no. 1) you should get zero volts key off and 12 volts key on.
The brown wire at the regulator plug is where you should get 12 volts key on and zero key off. Then it is jumpered to the alternator no.1 via the white wire in the regulator plug
to the no.1 at the alternator plug (white wire).

The red wire is 12 volts constant at the regulator plug and at the alternator plug no.2
via the blue/red wire.

The reason you got 8.2 was because you measured it plugged in and there is a 10 ohm resistance in the brown/white wire from the key switch. So your readings are where they should be.

That appears to be one of those jumpers for the regulator plug and it seems to be working, so you might as well keep it.

Here is what it does.

Attachment 1688360

here is how I do it.

Attachment 1688361

Re: Alternator with internal regulator
 

So do I not need a ground wire as shown in your first attachment VetteVet?

It's definitely appears to have a battery drain, it was 11.45 this morning after charging it a 24 hours ago and driving it roughly 40 minutes.

Gotta start pulling fuses I'm guessing and see if I can find a constant drain.

Thanks again for all the help fellas

Re: Alternator with internal regulator
 

The SI alternators ground through the case to the engine block so the internal regulator is automatically grounded. The old style regulators had to be grounded to the sheet metal and to the alternator bodies in order for the points inside the regulator to work. While it won't hurt anything to have the ground, it isn't necessary.

You do know how to set up the drain check where you disconnect the negative battery cable and connect a test light or multimeter between the battery terminal and the negative cable? If you have a light, or read more than .004/4 milliamps. you have a drain.

You want to check all the key off stuff first, so disconnect the alternator, the horn relay, look for any lights on. Stereo amp or radio etc. Don't forget that older batteries can go bad internally

Re: Alternator with internal regulator
 

I have run a drain test on other vehicles, but thanks for the advice.

The battery is brand new and I had them test it as well.

Re: Alternator with internal regulator
 

I figured you knew how to do the drain test, but I like to post it anyway for any readers who might not know. You said you were drawing 8.2 volts at the alternator on the white wire with the key off. You should not be getting any draw there with the key off. Do you suppose that the jumper from LMC is connecting it with the red wire in the external regulator plug instead of the brown wire which it should be jumping.Try unplugging the LMC jumper from the external regulator plug and see if the drain stops.

The correct voltage at the alternator plug is 12 and 12 with the key on and 12 red and 0 white with the key off . This is with the white alternator plug out of the alternator.

Re: Alternator with internal regulator
 

I'll double check these tonight,

Before I got 0 and 0 when I pulled the white plug.

I got 8.something volts on #1 plugged in
11.9 volts on #2 when plugged in.

Re: Alternator with internal regulator
 

So pulled these numbers
Key off
Big red 12.5
Sm red 8.9
White 12.3O uh

Key on
Big red 12.3
Lil red 11.7
White 12.3

Running
Big red 12.0
Lil red 11.4
White 12.0

Lights on
Big red 10.9
Lil red 10.1
White 10.8

Replaced the new alternator and got these.

Key off
Big red. 13.11
Lil red 0
White 13.1

Key on
Big red 12.69
Lil red 12.05
White 12.65

Running
Big red 14.6
Lil red 13.5
White 14.6

Lights on running
Big red 12.4
Lil red 11.3
White 12.25

Even with the alternator removed and all the under dash fuses removed I still had the light on for my drain test. I could also notice the battery draining when not on the trickle charger just watching the multi meter.

Re: Alternator with internal regulator
 

......................

You need to go back and look at post 2 and pull that adapter and see if the drain stops. Then check the brown wire on the regulator plug for the key off volts of zero and key on volts of 8,2 plus.

The little red wire should always be the same as the battery voltage. I'm puzzled why you got zero on it at some points unless you pulled the jumper plug when you checked it.

When you disconnected the alternator wires and the drain stayed it might be because the red wire in the regulator plug was jumping to the brown wire and feeding the key switch and the ignition wire. Have you had any problems with the engine running after you turned the key off?

Re: Alternator with internal regulator
 

I'm not sure I got which plug correct, apologies for making you guys repeat yourself. So starting over

removing the lmc adapter plug key off measured at the factory plug
WHite #1 0 v
Blue #2 0v
Big red 12.5v

Key on at unplugged lmc
#1 white 0
#2 red 0
Big red 12.3

Lmc plug in, alt plug out key off measuring at alternator plug
Number one white 12.6
Number 2 red 0
Big red 12.5

LMC plug in alternator plug out key on measuring at alternator plug
Number one white 12.5
Number 2red 11.9
Big red 12.5

Thanks for the patience folks
So I'm guessing I need the rewire number one and two wires because they're backwards

Re: Alternator with internal regulator
 

Switched 1 and 2, it's making more voltage and there is no drain when off. Also now 2 is always hot and 1 is key on hot, thanks

Re: Alternator with internal regulator
 

Sounds like a winner!