K10 Air Conditioning Condensation Leak to Interior

[GaK10]

I’ve seen quite a few posts but haven’t seen this particular line of questioning. What actually causes the condensation from the evaporator housing to run back into the interior? I can see water flowing out of the housing and down into another hole.
Is there supposed to be a pipe or hose that protrudes from the evaporator housing to prevent flow back? The rain I ask is because on my 2004 duranas, there is a pipe that protrudes from the firewall keeping the condensation from running from the drain back into the cab (accidentally broke it off and fixed it with a Bic pen).
I can see where the carpet is wet but the start of the wetness begins say mid ways on the foot rest (ramped part of the cab) and not from the top. There is no loss of coolant so I’m ruling out the heater core. Does anyone have a picture of the bottom of the evaporator housing? I need some help!

 

[GTX63]

Yes, there should be a drain hole near the firewall that allows condensation to empty out. It is likely plugged and causing it to back up into the passenger compartment. The unit shown in the photo is from a 1978 C10. Go at it from below with a small pick. It should come out pretty fast when you clean out the clog.

You must be registered for see images attach

 

[GaK10]

so there is no special pipe or fitting, it’s just a hole? There is water coming out but it’s running back to the firewall (out the drain). I’ll pick it out again, maybe something is letting it come out and build up.