Alternator question

Hello I have a 91 vr4, I've had it for about 9 months and never really had any problems with it until about 2 weeks ago. I never had any alternator or battery issues before like it always started fine and never died, but then one day while i was driving it, all the warning lights on the dash started flashing and the car wont rev over 2500. I unplugged the battery for a while and let it sit there and then tried to start it again but the battery was completely dead, so I put in a different battery, started it and checked the voltage and it read almost 18 volts. My friend had a rebuilt alternator from his 1g that he never used so I pulled mine out and put that one in, started it up and everything seemed to be good, the volts were at 14.5. I drove the car throughout the night while checking the voltage every so often just to make sure and it always stayed. When I got home I checked it one last time and it was still 14.5, the next morning I started it up and noticed that the battery and brake light were dimly light up, checked the volts and it was down to 12 /ubbthreads/images/graemlins/frown.gif and also when it was running the idle sounded really rough except it was sitting at 800rpm with no surge or anything and also when I shut the car off there is a noise coming from the back of the car that sounds like the fuel pump and it doesn't stop unless I disconnect the battery. Now my question is could the alternator took a crap over night like that? and why would one over charge and the new rebuilt one not charge at all.. I hope that all made sense and thank you from anything you can tell me.

 

[ktmrider]

Welcome, learn the search function as this is discussed all the time.

No the car did not destroy the alternator the chain store rebuilt alternator is likely crap.