Replace if ripped or missing.
Generally it can be mended if torn, most tapes don’t adhere to poly sheeting, Tyvek does.
Why you need it - If your window rubber wiper seals have shrunk excessively (they all have some space in them) over the years, rain and wash water will flow down the openings at the ends, damage comes from water-soaked door cards, might even mold over if the foam anti-vibration strips on the door card gets wet, and if speaker cones are missing - they’re vulnerable to water damage as well, and not only that, debris will accumulate and block the door drain openings. Good to clean everything thing out.
Once the door cards get wet repeatedly they will crumble from dry rot and maybe even forming mold if they stay wet and warm enough.
The plastic in place also helps deaden a bit of the hollow sound too….I can’t hear my door ‘ping’ anymore. So it’s more beneficial to have this plastic covering than not.
I found mine were missing from a hack job speaker install, door cards were watermark stained but held up w/o any warping. I replaced speaker cones with foam, self adhesive aftermarket type and for good measure put plastic sheet flap to cover them too.
I used some 6 mil plastic drop cloth sheeting (probably the heaviest opaque sheeting available on the shelf) at Home Depot etc., with 10 mil being better. I cut out the pattern and used very tacky Tyvek tape to hold it in place. Even using Tyvek house wrap will work too. Butyl tape is good too, none at HD but I had tyvek tape readily available
Note in my photo, a flap has to be cut and folded/tucked into the lower door void and just beyond the opening, this way any water running down will be directed back inside the door cavity and out the drain holes. - like flashing, it alleviates any chance water gets through and trapped between door card and the plastic sheet, the door sheet metal is stamped and there’s a lip around the upper and lower openings, it seems any water running down would be directed around the opening but looking at the OEM configuration, a slightly longer flap is present.
I believe Pelican has the factory $$ or a generic $ precut sheets available. You just poke the holes where needed and fasten that lower flap. Butyl tape if you can find it by the metal roof section of Home Depot Menards etc.
You can see where the water accumulates near the lower opening and speaker w/o the plastic in place
