Voltage Regulator/Relay Problem.

Ok here is my story. I have a 2002 Chevy Trailblazer with a 160amp alternator and factory battery (test in perfect condition) I have serveral electronics in my car ie 3 amps (5000 watts True RMS US AMPS) 6 screens , Navigation, Neons, HID's (Hi/Low) pretty much most of the big stuff. I am currently redoing my interior so all the audio equipment is out of the car ( amps, tv, speakers) however in the last few days i have noticed soemthign wierd the vlotage meter on the dash has been floating up and down between 11 volt and 14 volts ALL the TIME UP AND DOWN UP AND DOWN. My first thought was shhh my alternator is going out ( I KILLED IT) so i hooked up a volt meter from the battery and ran the wire inside to monitor it sure enought the dash meter was correct about 11 volts to 14 up and down ALL the time. This morning i go to start my car and i hear a few clicks and everythign dies (lights alarm and the key wont even come out of the ignition) so i assum the battery is dead and the alternator didnt charge the battery. I get a Digital Voltmeter and put it on the battery . Soon as i put the volt meter on the battery i hear a few more clicks and then my meter starts to work and shows 12.5 volts. I take the meter off and go into the car and hte lights are on everythign is back to normal. i go to start the car and now the voltage is working perfect no drops or fluntuations in voltage.

Is this a voltage relay or regulator? Thre clicks i heard sound like a realy click not a starter click or engin click.

Thank you in advanced for the help ....