Audio Systems: Scosche Cap went haywire, alternator whine, battery gauge

Question
Hello and thanks for any help. My brother-in-law installed a system in my 91 Honda Accord EX last weekend. I have had minimal problems with the alternator whine, loud pop when key is turned off. Major problem today. I started the car and let it run for a bit. The battery gauge lit up on the dash. I popped the trunk and the Cap was at 17V and climbing. I turned the car off and checked some connections and all seems fine except a loose crimp ground wire for the cap. I temp taped it to see if that was the issue. No. The same thing keeps happening. I am afraid to drive my car because I do not know what is happening. I was going to take it 20 miles away to a well know car audio shop in my area Monday to get the amp fine tuned. Now I do not know what to do and could use some help. Any idea what is wrong or any direction for me to go in? Thanks Diana

Answer
sounds like you have a bad alternator , the regulator is gone bad and now is generating a lot of power, or high voltage anything over 15 can damage the vehicle computer.
if you have to drive turn on all the lights and ac at full , that will lower the voltage
good luck