[intrcptrbird]

I would tend to think that it could be the climate control. Most issues you said had to do with or could relate to the actual climate control. I.E. the fan not going off with the ignition on. The voltage meter MIGHT be caused by a short IN the module causing it to suck A LOT of juice. That would be the first place I would inspect. You can pull it out pretty easy and take it to a car A/C place and they can probably diagnose it for you. The puller for the module and for the stock stereo are the same fyi.