03 Prerunner wet floors

My '03 Prerunner has a problem with the carpet getting damp. It's most
pronounced on the passenger side, front and rear. It's not associated with
rain, and I had thought that it may be the a/c condensation leaking out into
the passenger compartment. However, the a/c drain tube is clear, and I've
not been able to spot any moisture coming the coil area. It does drip
through the drain outside of the truck. This truck stays on asphalt all the
time. My dealer has so far been unable to come up with a resolution. I
live in an area of the country that experiences relatively high humidity,
and a/c use is regular.

Anyone else seen this issue?

Glenn