Long story short, I bought a 98 Sentra (1.6L) GXE automatic with 90,000 miles. It had a rear break issue, and a strut mount needed to be replaced... So I drive it about 2 weeks and it wont start. Replace battery, good for about 3 days, then wont start. Replaced alternator 2 weeks ago... had been fine, now it wont start again.

I got the charging system tested at Autozone, battery passed, alternator passed, "regulator diodes" failed. So I now need to replace the much more expensive voltage regulator too.

Where is it located at? It looks super easy to change out... unless is it buried and hidden under half of the engine? I cant be lucky enough for it to be mounted to the firewall or near the fuse panel can I?

Awesome car though. Its the 4th Nissan I have owned and honestly, I doubt I will ever own a different brand.

Most voltage regulators are in the alternator themselves. I would take it to a shop that has a good charging system test procedure and get a second opinion on the "good" alternator.

Ok. I did what you said Maxima. Good thing I didn't buy that regulator. They ARE in the alternator, and the part I was finding, is the part you buy if you are rebuilding your own alternator. Apparently sometimes parts to rebuild things cost more than just buying the part already rebuilt? Thats kind of crazy to me.

Also I now know what is wrong with my car... Sort of. My charging system is in deed perfectly fine. When they were testing it they turned it on and off a few times and sure enough, it didn't start the last time and needed to be jumped again. Except the little tester was hooked up and the battery was holding a charge at 12.4 (I think, it was over 12 for sure though) volts. The guy said the starter should kick at anything over 11.7 volts. So they did another test, and my "starting system" fails. He said they could keep testing it but it would be 90 dollars for the first hour, and 75 an hour after that so I didn't have them investigate. He also said it could be a few things. My ignition switch, my starter solenoid, the starter itself, or corrosion/a short in a wire somewhere in between any of those.

Should I keep this open or close it and create a separate topic? In the interim I borrowed a booster pack from a friend... I just have to jump myself 1 out of 6 times.

Start checking for power and ground. Start at starter then to ign switch, just workeed your way through the starting system until you see irregular voltage.