My problem started last night. let me begin with my set up I have a seperate battery in the back its an optima yellow top it is connected to a capacitor and running three amps 1 for my highs, 1 for my mids, and 1 running my 3 subs. my alternator is connected to both my car which also runs my radio and audio battery that runs my system. I have been running this setup for 2 years now. well last night i turned on my car and my radio would turn on but my amps wouldn't. When i checked my capacitor it read that my yellow top was at 7.2. when i drove to my chicks house it went up to only 8.2. then when i turned my car off a liitle bit after it went back down to 7.2. My reading for my other battery (car battery) always stayed at about 13.5. My chicks dad checked the batteries and the meter read read both as low batteries. This morning nothing changed. So i disconnected the ground wire from my yellow top audio battery and started the car. that is when i noticed that my car battery had taken a second or two to go up to 13.5 i drove it for about 30 seconds to my cousins house down the street and the meter by then was between about 12.8 and 13. it really wasn't steady at just one spot, but when i turned on my lights to check if it would change the reading it did as normal that reading went up and then back down when i turned them off just like normal. I have never changed my alternator and my Z28 is a 00.

 

its not uncommon for it to have different readings its not always going to be steady, are you having trouble starting your car ?