> I took it to the rebuilders today and they did what appeared to be a beautiful
> job of blasting the outsides and rebuilding the insides. Other than the
> bearing cap, one would swear it was a new unit.
Hey Mark, are you saying they didn't replace the rear bearing ? That's odd ...
> I plugged everything back in and the same symptoms occurred. After a could of
> starts she was toast.
So it worked OK at first, and then went full-on again ?
> I think in my rapid testing of many options I managed to
> start her with the main plug on the alternator unplugged. Bye bye diode pack.
If this is a classic Delco, starting the engine with the alternator plug (the
two smaller wires) disconnected should not hurt anything at all. It just won't
charge.
> The battery connection is at battery voltage when ignition is off.
That's as it should be.
> The
> indicator wire is 0V at ignition off and about 0.4v lower with ignition on
> (when disconnected. If I ground the indicator wire, the dash light
> illuminates).
So you are saying that with the wire disconnected from the alternator, and the
ignition on, you measure about 0.4 volts less than battery voltage from the wire
to ground, right ? The drop will be the ignition current going through the
switch, your voltmeter should not be drawing enough current through the lamp to
matter. That still sounds OK.
What's important, and I don't see in your post, is what voltage is on both of
the smaller wires to the alternator, both while running and stopped.
> So now I have nothing coming out.
Ok, so now this is a new symptom, right ? Before you said it was going
full-output, now it's no-output.
> The indicator tab on the alternator seems to
> go to about 12.0 v when the unit is turning so the indicator doesn't light as
> it should since that tab should be pulled to ground until the unit fires up.
So it stays near ground until you start the engine ?
> Can anybody conceive of a wiring fault that could cause this weird situation?
I'm wondering if perhaps you managed to interchange the indicator and sense
wires. The #2 terminal on the alternator should always get full battery
voltage, while the #1 terminal only gets current through the indicator lamp when
the key is on. Reversing them would cause the battery to run down slowly, and
possibly cause the alternator to overcharge.
> Is there a short in the armature that would cause a normal alternator
> rebuilding shop to mis-diagnose a repair for a short time.
They certainly should have checked for this. That doesn't necessarily mean they
did.
Here's some diagrams that might help.
Randall
[demime 1.01d removed an attachment of type image/jpeg which had a name of AC
Delco alternator diagrams 150dpi.JPG]
[demime 1.01d removed an attachment of type image/jpeg which had a name of AC
Delco alternator light test flowchart 150 dpi.JPG]
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