On my drivers side window, the inner channel --- where the screen slides fore and aft --- collects water. I have an '02, 37' gas, Mountain Aire.
I thought perhaps a drain hole was plugged up. Not the case. I pulled out the plastic screen runner and no drain exists. The outside frame weep holes are clear.
I guess the rubber seals against the glass are not seating properly and allowing water to collect in this screen channel. It eventually builds up, in a downpour, and leaks onto the armrest.
We've had several "frog strangler" rains recently in coastal Maine and I had to put a towel on the window frame to stop the deluge.
I decided to do something about it---- Here's my fix.
I used a small Dremel metal cutting tool bit to cut a slot from the inner rail to the second channel (the sliding glass channel). I brought the cutting bit in from the second channel. The second channel is wider than the first channel. The second channel has drain holes that lead to the outside weep holes.
I did this on both sides , driver and passenger.
Maybe some else has this same problem and this fix might help you

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