Recently I purchased a stock 2004 Silver Marauder with 44,000 miles on it. I've had the vehicle about 2 weeks now and the voltage dips from 14 (seems normal range) to about 10/12 when stopped at a light etc. It's especially bad when any accessories are on like A/C or the defroster. The voltage goes back to 14 when I continue to drive. Sometimes when its down low it spikes back up to normal. Ford has run diagnostic tests and found nothing. The battery and alternator appear fine under their tests. Another independent shop ran tests and they too couldn't find anything. To date they're only suggestion is to install a 200 amp alternator and see if that works. There is no cost to me luckily as the car is under a special 30 day warranty. Anyone have any thoughts as if this might solve the problem or what might be going on? Thanks!