Another Tip: If your alternator light burns out in the dash, you alt will STOP charg
 

I was surprised to hear this, but if you do not see your alternator light (red light on 2nd guage over in middle of guage on 79 911 SC) turn on when you start your car, you should replace teh bulb asap. If that littlelight is blown, it no longer completes the circuit and the alternator will NOT charge! crazy eh!

thats interesting--thanks for the tip

You are spot on here. Warren can explain it (along with dozens of other guys), but it is part of the circuit.

It is inline between the ign switch and the D+ on the alt. If that circuit isn't completed it won't excite the regulator..............no charge. Lots of older cars ran like this. I watched a guy pull his hair out trying to figure out why an old Datsun wouldn't charge. Nobody in the shop liked the guy so we all just let him struggle.

usually it's not the bulb.