I have a 2002 L 100 sedan and lately there has been standing water on both side floor boards, it started on the passenger side. I used a shop vac to clean it up there was that much water. I thought maybe heater core so took off some panels around the heater core. It looks like its a condensation issue coming from a black box looking thing directly behind the heater core. I can see water dripping off/ from the black box. I am not mechanically inclined at all just seeing if anybody knows what the issue is and if the dash is going to need to be removed to fix it.....thanks

 

As long as you don’t have a sunroof then the drain on the hvac box must be plugged. It drains out in the engine compartment under where the a/c hoses attach to the firewall. In the middle down low, it is black plastic 90 degree bend pointing down.
Let us know what you find.