Replacing roof a/c gasketby Robert Flight
Leaking roof a/c gaskets can often be fixed by merely tightening the bolts holding the a/c unit to the roof. But, eventually, the gasket needs to be replaced. Forum member Robert Flight explained how to do that in a forum message.
This is a 2 person operation.
You need to take the entire a/c unit off of the roof. By that I mean disconnect the wires, unbolt all bolts, and lift it to an area next to the normal location. Be sure to use padding on the roof to protect the roof.
To remove the old seal you will need to roll the a/c unit on its side and peel the old gasket off. The gasket uses double sided tape to hold it to the underside of the a/c unit. The old gasket may not come off in one piece. Also the old gasket may stick to the roof. If so use a knife to cut in half. It is about 1-1/2 tall and square shaped. The electrical wires need to be disconnected to get the new gasket on.
Here's the underside of the removed a/c unit
When reinstalling I use a caulk between the gasket and roof to insure a water tight seal.
Here's the new gasket.
While the a/c is off, inspect the roof for any possible signs of a hole thru the roof and not thru the a/c gasket. I've had cases where the a/c unit had a long screw that created a hole (& leak) in the roof.