water leaking in from air conditioner

Hi moakie
We had the same thing happen from the skylight over the bed.
The first owners had made a dodgy job fixing the leaks with a poor quality silicone which then failed following a few off road trips.
We ended up removing the entire roof unit, stripping back the original glue, and re gluing in with a product called SIKAFLEX glue which can be bought from any building supply firm. This is supposed to be flexible enough and able to withstand the rough off road travel of the van.
Have not had any problems since.
Ian

Hi Moakie, I had the exact same problem and discovered the water was coming from the airconditioner, but not through any fault with the sealing between the roof and aircon.
What was happening is the water was bouncing off the roof at just the right angle so as to bounce up between the grille slats in the air conditioner unit.
In other words, it is a design flaw in the Dometic air conditioner.
What I did to overcome this was very simple. I cut a length of aluminium angle cross section about 2 inches high and one inch across. I put some sikaflex or silicon along the bottom edge of the 1 inch section and stuck it to the roof just near the air vents on the Dometic Air conditioner.
From memory it was about 18 inches long. once the glue had gone off, it never ever moved again, and it stopped the water ingress by stopping the rain bouncing up off the roof and into the air con. A very simple fix, but very effective.
Hope this helps with your problem.
Keith & Joan.

Also timely to check the air conditioner roof cover.
It is very thin fibreglass, held on with only 4 screws.
I've noticed hair-line cracks around two of the screws so in time I can see the cover eventually blowing off.
To reduce further vibration, I have added four more screws. The cover now has two screws on each side.
Suggest other might consider the same.
David