I have a stock stereo system. I recently had to tap and helicoil my alternator's post back into the alternator body. It has been working fine but lately my voltage needle keeps bouncing erratically by 1-3volts and all my lights flicker with each bounce. Anyone know what the problem could be?

 

The great thing about an altenator is that it is mechanically simple and easy to diagnose. 99% of the time they either work or don't. If you did some work to the pos post, take it out and check the contact areas. If they look clean, then the regulator is fried. If that is the case, I hope it's still under warranty. If not don't go to gm, take it to a mom & pop shop. They can usually rebuild it and even rewind it for better amperage for around 60-70 bucks.