Ahh. That would be the lock cylinder that turns the ignition switch. Those will not cause the problem you described. The alternator, ignition system, (spark plugs), and fuel pump all run on the automatic shutdown (ASD) relay. If there was a problem with the switch, the engine wouldn't run so we can rule that out.
The only way to know for sure what's happening is to measure the two voltages on the back of the alternator when the warning light is on.
Monday, March 7th, 2011 AT 12:38 AM