Hello,
From the original post, I read this to be an access dor not the front window, so I am answering it that way. Sorry if I am wrong.
When I first got my Camplite 10.0, there was a leak in the "generator storage" compartment that allowed rain water to enter the closet area. I determined that the problem was due to the door of the compartment sticking out too far allowing the rain water to soak the weather stripping and get inside. My cheap solution, and it works great, was to buy one of the pre-fab aluminum drip caps, like here http://www.vintagetrailersupply.com/Drip_Cap_p/vts-515.htm .
For my small door it was less than $5 plus I had to buy some good caulk stuff and stainless steel screws. All for under $20.
Del
Delos & Holly
2013 Camplite Truck Camper 10.0
2014 Ram 2500 Reg SRW LB
2012 Burgman 650