Glass shops are great at finding leaks
2008 ranger passenger floor leak coming from bottom of fuse plastic foot shield.

Below heater box in the eng compartment is a bundle of wires going through the fire wall. Where they come out in the cab the wires split, you will find that the wires are dry coming through the fire wall, but are wet where they split, thus the water is running inside the bundle of wires and dripping on the floor. I have not fixed it yet, may require pulling the fender liner to find where the wire bundle is coming from in the eng compartment and a little silocone will fix it.

Mold smell in truck/car
Air conditioning is conditioned air, that means hot air or cold air, an evapoator drys the air by removing water i.e puddle of water under the vehicule with AC selected. In some cases if you select the recirculation mode on your heater controls the air bypasses the evaporator and mold grows on the evaporator causing a nasty smell. Cure run the AC in any outside air source modes (not recirculation mode) it took about 3 months to kill the mold and the smell was gone. running the AC in the winter will stop all of the windows being fogged and keeps the AC seal from getting hard and leaking. AC will remove all the moisture from the vehicule cab
Ted