Originally Posted by dbeiler

This is your problem, right here. Your charge indicator circuit is faulty.

The charge light MUST come on and remained illuminated until the engine/alternator is spinning fast enough to create electrical power.

When you turn the key on, the ignition switch must send power to the charge indicator bulb. The bulb will illuminate because the other terminal of the bulb is wired to the field coil connection terminal of the alternator. The alternator ground cable and alternator field coil effectively ground the charge bulb. When the alternator is at operational speed (and working correctly) the field coil will be at 12.7+ volts. The charge light bulb will then extinguish because both - and + sides of the charge bulb will be 12.7+ volts. Current will not flow when voltage is equal hence the charge bulb won't stay on.

You must diagnose the charge indicator circuit fault. Either you're losing voltage to the bulb through the ignition switch, or you're losing ground through the alternator side. I'd recommend testing the following components:
Fuse powering the acc portions of the ignition switch, ignition switch, charge indicator bulb, alternator ground, and any wiring between these components.

Please don't replace any parts until the issue has actually been diagnosed. Any proficient automotive technician (not some Pepboys smoe) could have it diagnosed in 5 minutes. You could've easily paid for that with what you've spent on three alternators.

Some important things to remember:
If the vehicle voltage is ever under 12.65volts, the alternator is not functioning. The battery is handling all the current draw.
Alternator output is regulated by controlling the amount of current through the field coil. Hence, a high current is used to maintain 12.7+ volts at idle, and low current to maintain 12.7+ volts at high alternator rotor speed. When idiots underdrive the alternator pulley, the alternator rotor speed can drop low enough to produce 0volts. I'll spare you my rant on that subject.