1995 Cadillac Brougham DRAIN

1st AC/heat WORKS FINE. I need to know HOW to clean the drain and where to put the wire? I have removed the under dash panel and pulled carpet back.
On the evaporator box there is a fastner that goes through the firewall on the lover right corner of the box. There is a sponge like washer around this fitting. IT IS WET and appears to be where the water is coming from.
Under the HOOD I have found 1) an open pipe apx 3 8th inch under the two tubes leading through the firewall into the evap box. This open tube is very short and forced ac air comes out of it. I have also located, further down and under the evap box a metal tab that seems to have a flap of insulating material from the evap box that partially covers it. When I can move things around and somehow get some drainage, the water drains from here. It doesnt keep draining though. Go out on the road a bit and park and check under car, NO draining. But it sure IS draining INTO the car pass side and I think from the above mentioned fitting. I dont know where the dang hole is and IF this is the drain? Really weary of fooling with what should be a simple thing. HELP.