I have a 72 Monte Carlo, was breaking in my new motor last night, everything was going great, until I noticed some sparks from the back of the alternator, I put the positive wire on the terminal but forgot to snug it down with the nut and it was bounching around arching. I didn't want to interupt my breakin so I put a piece of electrical tape on the wire to hold it steady. Got the break in done changed the oil did a few other misc things, fired up the car, was going to do some highway breakin miles and I noticed the "Gen" is light is on, it started out dim, but now is bright red. I disconnect all the wires, including the positive lead from the battery reconnected everything, but the light is still on. I do need a new alternator as the bearings are sounding bad in this one, but I am curious if anyone has seen this before.

Assuming it's an external regulated alternator...the "GEN" light circuit runs thru the regulator.
That intermittent voltage supply from the loose wire probably cooked the diode trio in the alt.

Yep it in externally regulated. Time to replace the alternator?

Time to replace the alternator?
Yeah, looks that way.
You could just replace the trio but you mentioned a noisy bearing...

Yeah, looks that way.
You could just replace the trio but you mentioned a noisy bearing...


Yeah I thought it was the water pump that was noisey so I replaced that, but come to find out it's the alternator, when I spin it without the belt on It I can feel and hear it. Time for a new one.