I had the same problem with our 99 venture we found out that the drain hose for the A/C had come off and was draining inside the van.
If it's the front passenger side ,I would say your heater core is leaking .
check sunroof for leakage
better check your heater core.
You probibly have a bad heater core.
It probably has a leak in the heater core.
windsheild leaks
Heater core failure.
It is your a/c condencer ot should be draining out of the truck. the rubber line is more that likely clogged.
If it is coolant, a leaky heater core. If it is water, a clogged ac drain or damaged door gasket.
Its probably the antifreeze in your cooling system. There is a good chance the heater core is leaking. Check the front passenger side floor to see if it is wet.
If it is wet with engine coolant you have a leaky heater core.If it is wet with water you have a plugged AC condensation drain.
Water on the passenger side floor would be a plugged up AC drain. The drain is located under the hood, at the lowest point on the HVAC box on the firewall. However if the floor is wet with engine coolant, the heater core is leaking.