How to locate leak location ?

With lights it is usually the lamp assembly itself that's leaking, but remove it and lay some caulk in behind it, make sure the lens is properly sealed (use additional sealant if you must, I like a THINK line of GOOP for this, than wait 30-120 minutes and lay it back in a calk base).

Other leaks or leaks into the RV are a touch harder to find.

ETERNABOND without question,dont leave home without it.....tenn

Marker light mounting is an often overlooked source of leaks.
water enters behind the light and can run inside the walls and under the roofing and show up anywhere inside the rig.

Leak INTO one of the LED lights?

Or

Leak PAST one of the LED lights? Meaning into the wall of the rig?

We used Eternabond tape on our cap seams - side seams and around all vents and skylight and fans. It's been 4 years and nothing has leaked since. I would and will use if for any future problems, if there are any.

You would be better off getting Eternabond tape. Instead of roof goop

Well I believe I found the leak. The rubber roof has separated from the from cap. I am head to the rv shop to get some rubber roof seal and going to goop it in.

I like the pressure test, but seems like a lot of extra work. Well we have more storms comin thru so best get to work.

My LED lights were supposedly sealed shut, but several leaked.

The water didn't come from the trailer, but because the base of the LED was not glued well enough to the clear coloured part.

Several just had to be replaced, but one was so weakly glued together that I could pop off the coloured part, dry it out and epoxy it all back together again. It still worked.