Why is my roof leaking around AC unit?

[Jack West]

I recently purchased an '01 Bambi...brought it home, cleaned it up some, then with our first real rainstorm went out to check for leaks. I unfortunately found water dripping down thru the AC unit. I tarped over the AC unit and that stopped the leak....at least temporarily.

I removed the louvered plastic interior vent cover from the AC unit and felt up inside where the AC unit rests on the AS aluminum skin. There is foam rubber there...it was saturated until I dried it out.

Is there a gasket between the AC unit and the AS aluminum roof that needs replacement? Does the exterior of this joint (between roof and AC unit) get caulked; if so, with what? (I assume from other posts that the caulk to use would be Vulkem 636)

It is disconcerting to read all the numerous posts about leaks on AS roofs, but would like to start out right with my unit.....any help or advice you can give me about how to proceed to fix the leak around my AC unit would be appreciated........jack in NCal

[Inland RV Center, In]

Replace the AC gasket, that's between the AC and the roof.

You will have to elevate, or move to the side, the AC to get the gasket in place.

Andy