Brand new alternator, still wont charge!

[maketracks]

Ok. Short version: Zero alternator, for awhile. Cycling batteries.

Last night: NEW Alternator. Duralast. Installed in parking lot. STILL wont charge!

Battery voltage, after off charger: 12.97V
Volts when running: 11.95V...
The morning after. Battery voltage with 2A charger attached: 13.29V, and slowly climbing.

?????????????????? Stumped, and confused!

Please walk me through what to do? What could it be?

GM 4.3

 

[eljefino]

what year? Computer controlled alt? Does the battery warning light work?

edit, 94 astro van?

There should be a second wire between alt and battery + for the sense voltage.

Also should be a fusible link in the main fat wire. Check for +12v at the big alt lug with the engine off.

 

[JHZR2]

Sounds like youre not exciting the alternator. Or perhaps the ground is shot...

 

[LeakySeals]

Yeah need a year, make, etc. Probably a bad ground somewhere. any after market electronics?

 

[maketracks]

Edit: Battery voltage is now 13.36V and climbing.

Looking at it, I see 3 wires coming out of the back alternator. I also see a frayed wire, I wrapped it loosely around the nut.

The digital dash reads battery volts, but does NOT blink to indicate lack of alternator charge.

The voltage DROPPED on voltmeter at battery when running.

Could the battery be causing this?

 

[maketracks]

Originally Posted By: LeakySeals
Yeah need a year, make, etc. Probably a bad ground somewhere. any after market electronics?


It had a subwoofer ripped out. Not by me.

And, shoukd alternator be grounded? It isnt ATM, and three wires are off main rear post of it..

 

[racin4ds]

You should have two separate connections on the back of the alternator, there should be (1) heavy gauge wire on the nut (this is the output wire) and then you should have a small black plug with 1,2,3 wires coming from it, all small guage.

Yes, the alternator grounds through the brackets, it doesn't hurt to run an auxillary ground wire though...

 

[maketracks]

Hey, all. I found and fixed the problem.

JHZR2 was right: That disconnected frayed wire.. Was the "excite" wire.

Cant take pics but thank you so much!

And my previous alternator wasi likely fine. Now, new

 

[eljefino]

Glad you fixed it.

For the record, my q about the alt light was not a stab in the dark, it is a necessary part of older style field excitation. If that bulb blows, there goes your alt.

See if you can return your new part and get money back. Take it as a lesson in proper diagnostic procedures following. Maybe buy a service manual.

 

[Donald]

There are 2 smaller wires (sense and excite) and a larger (output) and ground.

Then there are self-exciting alternators (single wire).

 

[zzyzzx]

Originally Posted By: maketracks
And my previous alternator wasi likely fine. Now, new

Did it test fine when you brought it to the auto parts store for testing? I assume that you did that before you bought the new (or "new") alternator???

 

[Cinadra]

Idle Air Control Motor needing to be cleaned or changed out can that make your altornator not charge up the battery?

 

[GMBoy]

Originally Posted By: Cinadra
Idle Air Control Motor needing to be cleaned or changed out can that make your altornator not charge up the battery?


No

 

[Donald]

And don't reverse the sense and excite or it will charge OK, but discharge when the engine is off. Sense is always +12V, excite is +12V when the key is on.