I have a fifth wheel RV that needs a second roof mount AC unit to keep up with the solar load in OK. I have a new roof mount AC unit and the front roof vent is prewired for the unit. I have studied how to install the unit through several videos on you Tube and dealer sites. Problem is, they are always starting out repalcing an existing AC unit never on an existing vent.

I need to know if, and how, the sealant is removed from around the roof vent prior to removal of the vent and installation of the AC. I have a rubber membrane roof and the sealant around the vent is rather heavy.

 

try to contact the manufacture of the rv and see what they say.

 

You likely have a Dicor EDPM membrane.

Vents are generally installed with putty or a gasket under the flange, then the screws go in, and it is topped off with Dicor self-leveling lap sealant.

I've found one of those 7 in 1 type scrapers to work good. You want something with more of an edge and stiffer than a putty knife, but not sharp either.

Remove the lower trim, then get up there and pick the putty off gently, being careful not to stretch or puncture the membrane, remove the screws, and carefully lift the vent off, reaching in and pulling the membrane off the bottom of the flange as you go.

Be careful of what you use on EDPM. Anything with petroleum products in it can attack and swell the membrane. A cloth dampened with mineral spirits can be used to help clean up what you can't get picked off.

The AC unit will likely seal with a gasket.

 

I did this on a couple of campers with no problem. Do as Jeff said and clean it up real well. The new AC should come with a thick gasket, it doesn't need any sealant. Just sit the new unit on the gasket and place it over the opening. It should be wired for the AC, just tie the wires in and get it to cooling. Sure is hot in Ok. was up that way a couple of days ago, 105! Glad to get back to Alabama, only 95 today. Enjoy the extra cooling.