I have 1995 1500 Ram std cab with 138,000 miles. I've had the truck for about two weeks and driven in rain but seen any problem before today. After setting out in a very hard rain today I found wet floor on passenger side. Appears to be coming from cow area. Any ideas would be appreciated. looks like it coming in about 6 inches from kick panel. Jack holder under front seat was rusted and broke but no damage to floor board yet. Thanks in advance!

 

Is it coolant? Or just rain water?

Have a look under the cowl, at the base of the windshield.... see what things look like there.

 

For me, I had A/C condensate running back along the bottom of the discharge tube, through the firewall and under the carpet... the puddle on the floorpan would surge along the sill to the back corner of the cab during acceleration.
The degraded seal between the inside of the firewall and HVAC box was the cause.
Without pulling the dash and HVAC to replace the seal, I just put a 90° rubber elbow on the discharge tube so it dripped down and couldn't track back into the cab.

I had eliminated coolant, and spent a long time (pulling my hair out) looking for a rainwater ingress path, when it wasn't rainwater.
Pull the carpet back, stretch the soundproofing down a little, and tuck your finger into the hole there the A/C condensate tube goes through the firewall, and feel for moisture behind the soundproofing.

 

Thanks that make sense, the ac been on a lot lately. Ill check it tomorrow. Thanks again so much!

 

It was just as you said described. Gasket bad around drain , put hose to drain and its working fine now. You saved me a lot of time and trouble, thanks again.