The condensation that is supposed to drain out into that puddle under the truck when the A/C is running is not happening on my truck. Instead, it is leaking into the cab and under the carpet, which is getting soaked. Where is the drain and how can it be checked if it is plugged, or what is causing this?

 

RedRocket on my 97 2500 360 the drane is on pasenger side of the truck next to fire wall. It's black rubber hoze about the size of your thum mine got pluged up and smeald o so bad. I used campresd air to clean it out Good luck.

 

Another way to clean out the drain is to use a shop vac. Put the hose over the drain and it will suck out the junk.
Tom