my sons new saab

Ok, this shouldn't be that hard. The alternators been removed and checked (twice) at the local parts shop and the results indicate it puts out >14 volts. With the alternator installed, i only measure battery voltage (~12v) at the alternator output. The battery's been replaced with a brand new one (by the yahoo I bought this car from). I'm pretty sure the problem is in the instrument cluster as the battery light comes on real dim when the car is running and I only measure 6.1v on the excitor circuit at the alternator. I've already had some other issues with this instrument cluster with cold solder joints, so I'm thinking about taking it out again. Unfortunately without a schematic, I'm not all too confident about finding a problem. Any other ideas?

e_900se

i know this sounds silly, but has your son added any electronic upgrades? Stereo? Subs? anything that is not stock that could be using up all the battery