My Tour just started to give me this problem. When the engine revvs above 2.5k rpm, all the lights start to dim and the voltage starts to drop (I have a voltimeter installed on my car). The problem gets worse when it goes towards 3k rpm where it drops to around 12V or lower. It seems that my car still starts OK. But when I check when the car off today, the batter only has little over 12V. I'm not sure if that's caused by a faulty alternator or just the batter is going bad? I remember on my old Subaru, when the alternator went, it started to suck charges. Not sure if that's the case now though. I'm definitely not looking forward to replace the alternator in the driveway because it seems to be a worse job than replacing the wheel bearing. But if it is bad, I'll have to replace it myself because I can't dish out $500 to have someone to do it for me. The first thing I have to figure out first though is whether it's the batter or the alternator. Is there a way to check without taking the battery out of the car, or if that's the only way?
