Our 1999 F-150 is having some problems. It just loses all electricity and dies as it's being driven. We have replaced the alternator (twice, first time we thought it was because the new alternator was defective) but it still does the same thing. My dad's mechanics can't figure out what's wrong with it (not the brightest mechanics) Anyone know what could be the problem? What should we check before we spend a bunch for the dealer to look at it?