You can simulate rain by having a friend dump a bucket of water against the window of a door. This way you can check the insulated door panel clips (testing with door panel on) then the vapor barrier behind the door panel (with door panel off). Water should flow through the door, but not into the cabin.

I want to say that this type of water ingress is more typical with a rear door. Good luck!

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Previously owned: '03 4.6iS Dinan Supercharged