I have a 94 grand caravan, over 200,000 miles. The alternator works intermitently. When it quits charging the battery and I tap on the alternator it starts working again. Is there part in the alternator that I can changed to fix this problem without having to purchase another alternator? If there is what would that be? Thanks!

The brushes in the alternator are probably worn - the usual cause of alternator failure. I know there are repair kits sold ($25) consisting of new brushes and diodes assemblies which are supposed to just pop in, but I have no experience putting them in. If you are looking for a cheap replacement, I would suggest you check out what the junk yards want for one.

If you are in any way mechanically inclined then you should have no problem figuring out to replace the brushes. I suggest that being your first time doing this that you have a pen and paper handy to jot down the order in which you take stuff apart as this WILL save confusion in the end.