the jeep ran when i parked it about a month ago now i need to jump it to start it everytime. once i get it running and take the cable off it will run untill i turn the light on then it dies right away. any thoughts? and to why i dies as soon asi shut it off and it won't fire back up with outa jump? i was thinking alternator but i can drive it around for forever with out it shutting off or loosing power so its holding a charge but i got no clue any help???