On my 2004 3500 Savana, it is under the hood, under and just behind the blower fan. It is not a 'tube' per say, but rather a plastic black square formed tube, that snakes a bit downward, with a rubber flap on it's downward end. That flap faces the passenger's wheel, and has a weighted portion on it that keeps the flap closed. I'm having to clean mine out right now, and am finding maple seeds and mud (possibly wet dust) blocking the water from escaping.
The AC condensate drain on a 2001 Ram is on the firewall just behind and to the right of the ac drier. its hard to get to to clean.
Condensate forms on the AC coil as the AC runs for a while. AC units are supposed to have a condensate tube that's designed to drain the water. If the tube is plugged or otherwise damaged the condensate will back up and get into the furnace. To avoid damage you should make sure the condensate is draining properly.
The usual cause is a condensate drain that is plugged. You should be able to crawl under the car and poke something up through the drain to clear it out. Another possible problem is the drain pan is cracked or broken allowing the condensate to drip. This would require partial disassembly of the dash to replace.
The condensate drain is most likely stopped up.
Under the passenger side carpet at the front of the transmission tunnel.
Have you checked your drain to make sure it is not plugged?
Check the AC condensate drain, it's probably plugged.
if it is not obvious.look behind wheelwell cowl.
Condensate always forms on the evaporation coil and the amount of water depends on the dew point and the temperature of the coil. All air conditioner installations are supposed to include a drain line for taking the condensate away, possibly to a floor drain.
AC condensation generally drains from a tube located under the vehicle. When vehicles sit parked and running the AC, a puddle of water will usually form under the vehicle near the drain hose.
Your heater core may be leaking, the condensate drain of the AC might be blocked, you can have a leak in one of the windows, or in the intake plenum to the ventilation .
Blocked condensate drain hose on bottom of evaporator.