Water on passenger floor?

Tried a search,but........

I noticed in my truck yesterday that there was water on the passenger side rubber floor mat. It has been raining hard off and on for the past two days. The rug was not wet (as far as I can remember). I am trying to determine if the water is coming from the windshield or underneath the glove box.

Anyway to determine this?

Is it possibly the heater core?
What makes them go bad?
What are signs of a bad heater core?

If it is the heater core, how much are they and are they easy to change?

My X has almost 45,000 miles on it.

Thoughts?

Thanks,

Stone

PS: I have had the defroster on for the past two days due to the dampness out and shut the truck off with the defroster still on. Does that matter?

If it were the heater core, you'd have coolant, not water on your floor mats.

Really?

Nope, just water; no coolant.

Stone

I had that same problem with the car I had before the xterra. After a rain the passenger floor mat would be soaked. I got to looking around to see what might be the cause.
It turns out that the drain that was next to the intake vent for the multi-speed fan was plugged up with junk that had falling from the trees.
All I did was clean out the drain and the problem was fixed.
I don't know if the xterra has the same setup with the vent or not I haven't checked.
Hope this helps

Cool. Does anyone know if the Xterra has this?

Stone