Thanks. I think I will get a new belt for a little "Murphy's Law" protection.

FYI - For people with alternator problems reading this in the future...

I tested my alternator with a "clamp amp meter" (AC/DC 600 amp capacity) to measure amperage as well as a multimeter set on DC to measure voltage.

The test readings from both of these indicated ENTIRELY DIFFERENT results! The voltage indicated 12 volts DC at idle (indicating not charging). But the amp meter showed that the alternator WAS in fact working - just not enough amperage.

So if just using a multimeter to measure voltage, you might be mislead into thinking the alternator was not working. Best to have both test meters so you can see exactly what is going on.

Note auto parts stores do not realize that cars have circuits greater than 10 amps. That is the maximum capacity of the amp meters they sell. So don't bother going there to buy one (might inform them that cars these days have 15, 20, 30, and larger amperage circuits. Not to mention 80/100/150 amp alternators.)

Anyway you can get a 600 amp AC/DC clamp amp meter on the internet for around $80. Some are ONLY AC, be sure to get AC/DC!

Another fascinating thing I learned about the Mercedes/Bosch W126 car alternators is that the instrument cluster "Batt" light bulb MUST be at least 2 watts. If less, the alternator may not work!

Or if the instrument cluster "Batt" light is burned out, the alternator WILL NOT WORK!

This is because that batt light circuit provides + power [via a blue wire on my alternator] to the alternator "rotor" which is an electro magnet basically. That rotor needs a bit of electricity to magnetize it to get things going with the alternator - sort of jump start it.

This is called "excitation" or an alternator "exciter" circuit.

I'm still trying to find technical information [pdf/white paper type stuff] about the voltage regulators which are used in these alternators. The manufacturers of these regulators seem to want to keep all their technical information to themselves...