Hello,
The A/C in our 1991 B250 got a good workout lately. One thing I noticed is that it drips condensation for about 10 minutes after you turn it off. I've tried hard to find a drain but the closest thing I could find is the rubber hose that comes off the blower motor.
Is there a drain for the air box? The wife said she thought water was backing up enough to come into the passenger area near here feet!
Thank you, Steve

 

I am not sure about a 91, but if you look where the passengers feet are, way way back, you can see where the air intake for AC MAX is. I would look in there if you can get in there and see if you have leaves etc.
I just had this issue too. What it turned out to be fore me is my blend door rusted from the inside out. There were chips of rust everywhere inside the case. It plugged up my case.
The drip slot is right under the case. You can try to stick a stick up there or even a shop vac. In reality, (with my 03) you have to take out the case to clean it right.

 

Thank you for the reply. I haven't dug that deep into the van to see those parts yet. Is it possible that the slot you are talking about dumps the water into the front right fender? I was crawling around under there and noticed that the front drain hole on the fender was plugged with what appeared to be sea weed. I was able to free it up but we are past A/C season now so I won't know if it helps.
Steve

 

I really am not sure where it would drip out on yours, by on mine it drips out more where the lower control arm is than the fender

maybe some else here can help some more