Chevrolet Repair: water sloshing, drain tube, water stain

Question
2000 chev. tahoe i hear what sounds water sloshing under the dash, on the passenger side. Just recently started. What could it possibly be.
Thanks for your help;
Brian

Answer
HEy,
 
 The evaporator drain tube is plugged and not allowing HVAC water to escape.  The drain is on the passengers side by the frame.  YOu can generally follow the water stain to it.  Clean it out carefully with a pipe cleaner.  Be carefull not to damage the evaporator.

w