Don't know for sure about your truck since you didn't let us know what year, but on my '04, the drain is a rubber hose through the floorboard on the passenger side. Can only assume yours is the same since the carpet gets wet on the passenger side Could be a clogged drain line.

 

Could also be a leaking heater core. Check to see if you get the wetness with the A/C turned off.

 

Crap #FACEPLANT. Sorry about that.

My truck is a 2003 2500HD. Quad Cab.

I am not running the AC because it is too cold here in Portland, but I am running the heater. Could that mean the heater core is the problem?

There is a lot of wetness along that plastic duct work under the carpet.

 

How does the wetness smell? If it is a heater or hose leak it will have the distinctive antifreeze smell. Just because it is winter doesn't mean your compressor doesn't run. It runs to help keep your windows from fogging over.

 

how does the wetness smell? If it is a heater or hose leak it will have the distinctive antifreeze smell. Just because it is winter doesn't mean your compressor doesn't run. It runs to help keep your windows from fogging over.

+1

 

It smells like water. No antifreeze smell.

 

The a/c drain is the small rubber elbow located on pass side firewall just above the framerail. It is possible that it got plugged up.

 

Fixed!!

The passenger door seal was kinked when installed by the factory. The seal has a metal spine and that was bent. This left a gap between the mounting frame and the seal allowing water to run down the front of the door and into the cab under the carpet.

New seal fixed it. The new seal isn't an exact fit and the door is now difficult to shut without slamming hard. I should probably spend the $$ to get one from the dealer.

 

The passenger door seal was kinked when installed by the factory. The seal has a metal spine and that was bent. This left a gap between the mounting frame and the seal allowing water to run down the front of the door and into the cab under the carpet.

New seal fixed it. The new seal isn't an exact fit and the door is now difficult to shut without slamming hard. I should probably spend the $$ to get one from the dealer.

FourBeer - would it be possible to get a picture or better description of this seal? I have recurring issues with water from the AC leaking into my cab in an 04.
Steve