sloshing in blower
 

i have a 98 chevy 2500 p\u 5.7 vortec and i hear liquid sloshing around under the dash on the pass. side. any ideas? and what to do.
thanx, Dirty

Sounds like a plugged evaporator drain. If you can get under the truck, you will see a tube from the firewall or HVAC box. Try to dislodge the obstruction by inserting the erase end of a pencil or similar blunt object. Some drains have a 90° rubber elbow on them so it may be necessary to get the truck on a lift.
The only other sloshing noise that I've run across was with an air pocket in the cooling system and you could hear the coolant through the heater core.