By any chance, did you shut down with the battery cable loose or off? Is the engine ground strap loose, dirty or damaged?

When the engine shuts down, a powerful reverse current forms in the alternator coils. It dissipates into the battery if everything is in good shape. I think you'll find that there's a weak connection somewhere between the battery and the alternator. If so, the inductive kick would have nowhere to go, and the stator may be toast.

What you need to do is clean and tighten the battery cables, including the battery ground at the point it bolts to the body. Also get under the car, find the engine ground strap and make sure the connection points are clean. Then take the alternator back and act outraged at having received a dud.

There's a heavy elec. load that should not be there. Probably glow plugs are after glowing when they should not be.
I doubt the alternator self destructed in such a short time.

Yeah but the store clerks give you a funny look when you buy a quart of oil and a pair of ladies panty hose. :P

I tried a used pair of pantyhose on an old tractor many years ago, but it didn't work.
Maybe I should've tried a new pair, but my friend's mom wouldn't cooperate!

Happy Motoring, Mark

...no I didn't do that...but I did run the engine briefly with no connections to the new alternator (before I built the adapter harness) to test belt tracking with the new ratcheting pulley...that would cause the conditions you described...

There's no load that I noticed -- the battery voltage is stable at 12.04V on my multimeter whether or not the negative cable is connected (this is with the engine not running). It could be different with the ignition on. Revving the engine up to about 2000 rpm had no effect on charging -- all the dash lights stay on.

Coming from someone involved in the power generation industry, that is utter nonsense. This harkens back to the old myth that a generator running unloaded will build up a dangerous discharge of voltage and explode.

A self-excited alternator can run a vehicle without a battery connected with no ill effect provided that the load doesn't exceed its production capacity. I have personally started several cars without batteries using only jumper cables, then disconnecting and insulating the leads to move the vehicle and never had an alternator fail from that.

If the alternator packed up from a loose connection it was due to arcing at the battery lead causing EMF spikes flashing back at the alternator, or it was a POS alternator to begin with. I'd strongly lean towards the latter.

This is what I'm thinking as well. I am just outside the return period, so I'm going to order another one from the same vendor and return it on that ticket. I've had really good luck with DB Electrical in the past (folks on the Saturn forums order them constantly), but even decent suppliers have bad parts occasionally.

I'd do more tests before condemning the alternator since it was working for a short while after installation. Something tells me a new alt. from the same vendor will behave the same.

What type of tests do you suggest? There is continuity between the alternator and the battery, and the car is a 100% rust free west coast garage queen with all straps present and grounds intact.

I tested voltage at the alternator terminal, and it is the same 11.8v that I read at the battery.

I would check the excitation wire continuity to the battery lamp/ charge indicator and that the lamp is well seated in a clean socket. Is the excitation wire bolted onto the alternator or via a connector? If a connector, clean all the contacts. Did you rev the engine above 1500 RPM before checking charge voltage?

The lamp glows (and it didn't before the wire was connected). I revved the engine up, but it did not change the dash lights.

I'm going to go try again right now.

I cannot help but notice that your alternator problem happened on 4/19 and you posted that it was a mechanical failure. How come it morphed to be an electrical problem? It does not make sense as alternator R&R is straight forward. You need to go back to square one and see what you have or have not done.

Negative battery cable is disconnected:

The multimeter shows perfect continuity from the large alternator stud to the positive battery post.

With the ignition on, there is 3.8 ohms of resistance from the small post to the positive battery terminal (from the charge indicator bulb).

I'm going to go start the vehicle to see what the behavior this morning is with a fully cold alternator. I'll leave the DMM connected to the large stud to observe the charging (or total lack thereof) as the engine warms.

The main stud mounting point is broken internally. Alternator was FUBAR on delivery.
:mad:

That'd do it. Did you over tighten the nut on the stud? That stud is on an insulator and the torque should be just tight enough so the nut will not undo itself. Probably not more than 1 to 2 ft/lb.