I have a similar problem with my AE92 Seca, where I discovered dampness in the front passenger side 2 days ago. I was rather busy and at the time didn't think it would be a major problem, the following day I discovered a substantial puddle, at the front, with the rear passenger side also now wet. It has been raining quite a lot these last few days so I'm guessing it's the rain, especially with that kind of water. Upon some research it's possible that it could be rainwater seeping in through the A/C line somehow.
Other issues are I've had my rear de-misters on quite a bit along with the a/c on full heat going up to the winscreen because of all the clouding up I had in the car, not sure if that also collaborated in the mess. I'm getting mine checked out at O'Brien's on Monday, until then it's in the garage drying out...hopefully this will be solved on Monday if it's a windscreen seal problem.
Sorry to hijack the thread, but I figured with both our problems happening in a similar car at the same time, might help us both with any info. Did you check if the sloped part of the floorwells were wet? That is to say the slope under the dash? Mine weren't, and I can't figure out where the water is routing in from.
