86fc_Driz

Ok guys... here's my dilemma... I recently replaced the alternator on my car (2nd alternator in 1 week) and the battery (Optima Red Top). I am getting power TO the alternator but it's not feeding power back to the battery to charge it. My voltage is very low as you probably would have assumed. I can't seem to figure out what the problem is. My question is, Is there some sort of a diode that regulates the electricity flow? I metered the voltage on the post and it had voltage. Also... I had the alternator tested and it tested fine! Shoot me!

HAILERS

The large terminal on the alternator has batt voltage on it all day long. It connects to the battery thru the MAIN fuse in the engine bay fuse box.

It's the small plug on the alternator you should be interested in.

Put the key to ON engine OFF. Pull the small plug off and see what the voltage is on the small plugs TWO wires. Each should show approx 12vdc.

Now put the small plug back on the alternator. Backprobe the WHITE/BLACK wire. It should have 1-3vdc on it. Does your's?????????? or not.

Don't mistake the White/Black for the Black/White when doing that.

IF one of the two wires on the small plug had no volgage on it(them), then say so. It's unlikely since the Black/White comes off the Engine fuse and the car won't start without a good engine fuse. The white/black is fed by the Meter fuse and you'd have no gauges working if that were so.

This only takes about ten minutes to check out.

You need to idle the engine and then check the voltage at the alternators large terminal and see what it is. Even rev the engine to about two grand and check it. It should be 14.3 - 14.7vdc or close to that.

86fc_Driz

Ok I JUST got inside from testing this car as it was dark yesterday when I first posted... with the key ON and engine OFF... The 2 wires both ready slightly less than what the battery voltage read ~10.7vdc

When I backprobed the WHITE/BLACK (not the Black/White) it ready roughly 1.2vdc

When I metered the large terminal on the alternator it also read slightly less than what the battery read.. HOWEVER when I revved it the voltage would slowly climb.. but if i left it at the same rpms the voltage would begin to drop again and when I let off completely it would drop back down to ~10.7vdc

I even tried this "revving procedure" by testing directly from the battery - Same results which i would assume is typical.

HAILERS

Do you have one of those *underdrive pulleys*?

Odd. Your getting the excitation voltage on the White/Black. That's good.

Can you swap in a battery from another car and try again? I'm NOT saying it's the battery, but I'd give it a try. I don't understand the low rise in voltage as you rev'd it. When you rev'd it and the voltge went up......how high did it go?

It sounds a bit like the regualtor in the alternator is'nt doing its job very well. Any way you can take the alt off and take it to a Autozone or???? and have them check it for free?

I re-read this thread. Two alternators recently. Heck, you've got the right signal/power on the small plug and your measuring the output AT the large terminal of the alternator, so I say bad alternator.......again..??

The alternators guts get their ground from the alternators case. So the two places the alt case mates to the engine should be clean i.e. the adjustment bracket. That's not likely the problem. Just common snugging the bolts down should have done fine. Not the likely cause.

Have the place you bought it from check out the alternator if they have that capacity/ability. A rebuilt alternator shouldn't be doing this. Your car seems ok (wiring).

Oh, it seems you already have a fairly new battery so that should n't be it.

86fc_Driz

Yea... The battery I originally replaced was an Optima Red Top as well and that was only 5 months ago... just replaced it 3 days ago...

NO underdrive pulleys.

Yea, I'm on a first name basis with the guys at Advance Auto and they are telling me that it may be a ground... So I bought a ground strap aaaaaaaannd... still nothing...