I need to know how to undo the headliner to access the rear sunroof drain. Then I could try to clean the drain pipe from sunroof and down to the rear wheel.

 

Yes, I just reversed it. At beginning, the rubber seals are facing inside, toward the battery. It was very easy to remove at first. However, after I reversed it, it is like impossible to remove it. So I have only the pic of after reversing.

I just checked today, there is no more water leaking into the battery bank after a car wash. But I am still curious that what would happen to the water on the other side of the rubber seal. It doesn't seem there is an exit for water in the room in rear.

To me, the original placing of the rear ventilation doesn't do anything.

 

It seems to me that the drain holes on my car are not clogged up, but water still gets into the battery tray, that's why I reversed the rear vent. I did water test on the sunroof.

Or, do we have to unclog the four drain holes every month to make sure it is clean??? That's just silly...