2008-2013 Water from HVAC drain in passenger floorboard

[Dan Clark]

I have a 2008 GMC Sierra 2500. Lots of water in passenger side floor. Checked everything I could think of. HVAC drain is clear and draining well. Sprayed hose all over windshield and all possible entry points. Ran truck on wet roads with no active rainfall to eliminate the possibility of water splashing in. No luck. I spent a lot of time diagnosing and saw nothing about this on web. The condensate drain elbow was missing, leaving a one inch straight tube coming through the firewall. Surface adhesion was leading the condensation back through the firewall via the outer wall of the condensate drain. Check to make sure there is an elbow. Such a simple fix, but ridiculous diagnosis.