ac delco 12si terminal wiring?

[mumphra]

alright just ran the engine with all electronics off it runs at about 15.5 v with them all on it runs at about 13 battery when truck is off it shows just above 12

 

[mumphra]

so should the alternator ever be putting out more than 15v or is that a proper charging range?

 

[Steamer]

Are you sure you're getting and accurate reading? Are you reading the voltage with a decent multimeter or are you using the dash mounted gauge type voltmeter? 15.5 V is a little bit high. Somewhere in the mid 14s is about right.

 

[mumphra]

I have a fluke 789 and I am checking it at the battery. I am a low voltage control systems engineer who designs low voltage systems and troubleshoots them. I am not a rookie at this stuff and this is killing me. I have spent hours and hours trying to figure this out. as an update I get 14-15 all day until I turn on electronics(then 13 to 14). It is not doing anything with the rpm's now so its constant. If there is a test I can do with a multimeter to test the regulator (resistance) that would be great or someone who really understands the inner workings of the 12si I would love it at-least to rule out the regulator. DAY 3 SOMEONE PLEASE HELP!

 

[mumphra]

still an issue if anyone has insight

 

[pbgbottle]

whats the voltage at the fuse block instead of the battery when it is runnnig is it 15 volt there too ?
i'm just thinking out loud .

check this out .half way down at the diagram about the sensing wire and the alt boosting the voltage .

http://bob_skelly.home.comcast.net/~bob_skelly/alternator_conversion/wiring_alternator1.html

 

[mumphra]

voltage at fuse block is 14.5 when volt gauge is reading 15 and when i turn everything on its 13 when gauge is reading 12

 

[Trollhole]

 

[Steamer]

If your sensing wire, term #2 is connected to the big lug on the alt as the picture shows, (and I think you said it was) then you should be reading voltage with your meter at that lug on the alt. You could have a voltage drop at the fuse block. You're reading the voltage drop with the meter but the alternator doesn't sense it. Try running that sensing wire to the fuse block even as a temp just to test.
In short, sample the voltage with your meter where the alternator samples voltage.

 

[Poser]

voltage at fuse block is 14.5 when volt gauge is reading 15 and when i turn everything on its 13 when gauge is reading 12

Sounds normal.

 

[peesalot]

Poser, help me understand why the diode is inline on the wire that connects to ign. ? What is the effect if that wire has no diode ?

Nevermind, I figured it--- engine keeps running when ign. is shut off due to the back feed of voltage thru that wire. I guess that is why my old 12si had that wire going to the acc. terminal of ign. with nothing else , that way it worked as if a diode was in place.

 

[mumphra]

diode in or out no change for me engine turns off fine...

 

[mumphra]

I guess I am going to just run it for now and later if its an issue Ill replace battery and alternator