At some point while driving, I realized that my voltage had jumped up to 16 volts. I quickly spun the car around and drove it home maybe thinking something would short and I would be stuck. Got it home and saw that at idle, the voltage had dropped to around 13. Anytime I reved it up, the voltage shot up. Is my alternator going bad or the voltage regulator?

 

That is definitely your voltage regulator. And unfortunately the voltage regulators are internal to the alternator on our cars. Your best bet would be to replace the alternator, and not drive the car until you have it replaced. All of your electronics are rated to run at ~14.5, and I know from personal experience that the ECU does not like to have much more than that thrown at it.

 

Pull the small plug off the alternator. See if the BLACK/WHITE wire has 12vdc on it or not. Key to ON when doing that.

The other wire, WHITE/BLACK should have 1-3 vdc on it if the plug is ATTACHED TO THE ALTERNATOR and the key is to ON, engine OFF.

Say you go to start the engine. You start it but don't put any throttle inputs to it to drive the rpms up. So now your idling at 700-800 rpm. Where is the volt needle is one question I'd ask and the other question is, if the needle was close to the 12vdc mark and you gun the engine to say over 2000 rpm, did the volt needle suddenly jump up to 16vdc? Say after you reached 2000 rpm is what I'm driving at. IF so, I'd suspect one of the two wires on the alt isn't making contact.

Then again, you should be using a digital meter to see if the voltage AT the alternators large output terminal is reading right i.e about 14vdc to 14.2 vdc at say 1000 rpm or a bit less..

 

i have the same exact problem and i just put a new alternator on my car last week and i'm going to get a new one tomorrow so i'm going to find out if will fix the problem. i have been having trouble out of my alternator since last summer and i haven't had the money to buy one so i had the old one rebuilt and it did great for about 3 months.