how to fix or change a alternater on my travers

Hello, The vehicle will need a starting and charging system test. Failure to crank may be caused by many items, such as: -Bad battery -corrosion on battery terminals -failed battery cables -bad starter -bad starter relay -Bad ignition switch -anti-theft system issues and the list could go on. It is a a little unclear what is going on based on your description, and I would advise the starting and charging system check to definitively state the solution.