Alternator not charging battery

[Tico Frank]

So as the title states my alternator is not charging my battery. I have removed the alternator and it was tested a good. I have an alternator with just 2 connections on the back. #1 is a large post with a nut and #2 is a smaller post with nut. I have wire 1 and 25 connected in the harness and my cluster is connected. A friend of mine has an alternator with a clip on the back (just like the clip for the ICV) but mine doesn't?

Any ideas?

[e30austin]

Did it all work before? Maybe something in your wiring?

FWIW, all my alternators have been two post, two wire alternators, with no plugs/clips.

[hooken m]

voltage regulator?

[Tico Frank]

^^If the voltage regulator was bad would that have shown up in the test at autozone?

[hooken m]

^^If the voltage regulator was bad would that have shown up in the test at autozone?

im honestly not that sure. i dont want to give you a wrong answer, but its a pretty easy part to replace. normally if your alternator and battery are good and your system still doesnt recharge i would say its a voltage regulator

[MF DOOM]

add a ground from your alt to chassis. boom.



And neither of those wires is a ground so dont connect it from there to the chassis or youll have more issues to deal with.

[Tico Frank]

Can I ground from the mounting nut that holds the alt on?

[Gregs///M]

Can I ground from the mounting nut that holds the alt on?

Yes, there is usually a hole or stud to attached a ground cable. Do not use the isolated output cable that goes to the starter. Do not use the small stud, that is for alternator excitation.

The blue wire must show 12V when the car is running, this triggers the alternator to charge.

GL

[328ijunkie]

Alt ground is unnecessary on 24vs

[Tico Frank]

So are alt grounds necessary or not? I just tested the battery with the car off and it was 12.75ish. Then I tested with the car running and it was 12.45 or so. So obviously the battery is not getting the necessary charge. I looked at the battery light on the cluster and it comes on when I turn the key then turns off when running so I think the exciter is working. This is like the last step before I send this car off to have the exhaust done so help me out please folks.

[Cyrix2k]

Make SURE your alternator/charge light in your cluster works. It should come on with the key in run & the car off. If that's good, check your C101 and failing that, there's a connector under the dash. Make sure your D+ is being energized. As long as the engine is grounded well (sounds like it's good enough since the engine runs), you're fine. No dedicated alternator ground is needed.

[Tico Frank]

Yep the charge light in the cluster comes on when I turn the key and turns off when the car is running. I think I disconnected something under the glovebox because I have an 87 and if I remember correctly there was something I still need to hook up there?

[Cyrix2k]

I don't know, there's nothing on the glovebox side on my '85. It sounds like your battery isn't correctly attached to the alternator to me. You should have the battery's positive terminal connected directly to the large terminal on the alternator. The behavior of you charge light makes it sound like the regulator & alternator are working.

[JAYMAC]

DO you have a meter? See if you can get a reading right off the alternator to the frame. See what kind of volts you get right there. Check your ground wires. Battery cables clean and tight. Did you check the battery for a bad cell?

[MF DOOM]

Alt ground is unnecessary on 24vs

If they ground through the engine, like m42s, then it may be necessary. Its worth a shot and its easy to try.