I recently had a new dash put in my 94 2500. I do not often have passengers, so I did not notice until the other day that I had water in the passenger side running from the drain on the heater/AC unit to the floor and exiting at the running board. I seem to remember this problem from years ago and the fix was easy, but of course I have forgotten. It was a clog somewhere. I have felt the drain nipple and there is no hose there. Sounds like there should be. The local guy says just blow out the nipple, but that does not sound right. The shop manual says to be sure to align the heat/AC unit correctly or water will drain into the passenger side. Well, it seems to be aligned, but how can I tell? Is it supposed to have a drain hose attached to the nipple (engine side of firewall)? And how do you "unclog" the line? Of course it is possible that the new dash installation has nothing to do with the problem, but seems likely.