Water leaks on the passenger side carpet when i run the air for an extented time on my 04 gmc envoy

The evaporator for the air conditioning is under the dash on the passenger side. Open the hood and look on the firewall for a rubber hose that sticks out of the firewall. This hose is to allow the water to run outside and onto the ground. Sometimes they plug up and the water can't get out so it builds up and drains onto the floorboard. Hope this helps...

You have a busted heater core under dash this is going to get expensive
Simple fix find the two hoses going to fire wall get a hot water coupler and attach together with hose clamps for now it will get you buy till you can get the heater core fixed
The heater core must be removed from inside the cab
It requires removing dash to get to heater core
The labor alone from just book quote is five hundred not including the parts price which can bump it to almost a thousand