intermittent alternator charging

intermittent alternator charging


Mena, AR
1976 CJ5 258. MC2150 carb, PSC steering, Team Rush upgrade, 1 piece rear axles, all electronics relayed. Coming soon: Herculined tub, camo paint- and a bunch of filthy, muddy kids!
edit: sorry guys, 76' AMC 258 i6 / 4.2l .

My alternator likes to stay around 12v after start up, occaisionally it stays there but usually after a little revving or driving it goes up to around 14, sometimes it just stays there. Hooked up my DVM to it while idleing, driving or revving and get the same reading so the gueage is right. All connections under the hood are new and/or clean.

Alternator going bad? Is there a way to safely test the alt at home?
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Yeah I should have done that before I posted here, but here's another detail my son just called me about. He's been tinkering with the problem and noticed that there is a significant drain on the batt only when the ign is on, with and with the engine running.

Can you think of anything outside of the alt that might cause this? I'm thinking that it could also be in the alt, but when they begin to go bad they just get worse and worse. With this problem it comes and goes. He noticed that the voltage rises and falls with the rpms occaisionally.
Yeah voltage regulator in the alt. Well I guess I better rule it out and take it in.

That'll at least get me started on the problem. If my boy figures it out before I get home I'll never hear the end of it, and he just might do it too- the tyke. They are all so excited about hitting the muddy trails.

Thank you for your help.
Well I noticed something from the guage site about my alt set up. In the diagrams it has a ground connected from a bolt hole in the alt housing straight to the batt. I just assumed the alt grounds itself through the engine bracket, which I'm could be bad.

Does anyone here use that bolt hole and ground to the batt? Another thing to rule out when I get home.

Catch 22- if the alt is bad I'm out of at least $60, I'm sure, but problem solved.

If its a harness short then I end up losing my hair and have to buy Prozac or some moonshine trying to find it.

Good grief.
No not yet. On the road right now working for the r.r.

Trying to get her ready for the warm season. Hard to do when you're on the road. But with this forum I can research and have a set plan when I get home. My son is helping out too while I'm gone. Should be blasting the inside clean for the herculiner we're gonna coat it with.

If its the alt, and everything points to it- I've decided to go with a Delco 1 wire. I'm mental when it comes to neatness and I'll do anything to eliminate wires.
I think you are on to the problem and I agree it sounds like the alternator. When you get home remove it and have it tested.
If I were you I would avoid the one wire alternator. They are more expensive, they don't activate the alternator warning light. Their only advantage is they are easier to install. You can have the extra connector dangle. If you like neat wiring what would you do with the other connector? Remove it with it's wires?
Check out this link. I don't see any reason to spend money on a one wire alternator.
Or this link:
How Alternators Work!
Oh, one last thing: before you remove the alternator make sure the belt is not too loose. A belt can slip after the engine starts and after a while can start to spin the alternator.
I'm glad you replied about the 1 wire. Didn't know about the light. I'll take it off and just get an OEM then. Don't have a need for more than the standard output, and an occaisional use of the k.c's won't draw down enough to need more.

Do they still call em k.c's? Jeez its been a while.

Oh, good tip on the belt slipping. Its easy to get caught up and break the Door down when it was unlocked and didn't think of turning the knob first......

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