I drove a lovely little girl in a Home Coming parade last Tuesday evening. Car was running great. Still had oil in the engine and I'm 50 miles from home, at night, on the Natchez Trace Parkway. Somewhere, before I got home with the engine running well, the alternator light failed. If the light fails while the engine is running you have no way of knowing. About a mile from home the headlights dimmed...nearly went out. I got to my neighborhood and the car began to buck and snort, obviously the battery was about to give up. I turned off the lights and was able to drive into my garage.
Next day I installed a new alternator, started the engine and no juice. Everything is wired correctly, must be a bad alternator. Exchange it and installed the new new alternator; no juice. By now I'm really frustrated. I had that alternator in and out 4 times checking the wiring ( what is the definition of insanity?)
I woke up this morning at 6:00, that's 4 a.m. California time, and knew what the problem had been all the time. The idiot light was out. I pulled the light and it was not burned out, but had been displaced in the socket enough that a good connection was not made. Now the idiot light is on; start the engine and I have 14.5 volts.
This may not apply to all alternators. My car has the 911 shroud ans run a Delco CS130 alternator. The mounting brackets are machined off to fit inside the 911 fan.
I was really dreading the failure of the alternator because I suspected that the installation would be a bitch, but it wasn't. I could have been finished in an hour.
Beware of the Alternator light!