RbelXJ....I have the same thing going on with my 87XJ. It's not coming up from the underneath, because it happens when it's just sitting, so I'm thinking it's from the winshield too. Luckily, or not maybe, a sheet of ice flew off a car in front of me on the highway and smashed my windshield, so I have to replace it anyway, hopefully that will solve my leak. I'll let you know. I am just about to try the hose technique also, I did it on the pass window and saw nothing, windshield never occured to me.

I also have the problem with the heat on the passenger side floor, but the driver side gets pretty hot too, I just chalked it up to the exahust running directly underneath it....and it being 20 years old. I don't put too much thought into this thing, it just keeps going with 165K on it and I don't ask it too many questions.