When I turn on the heater after a heavy rain or a car wash, water sometimes pours out of a seam on the bottom of the heater box under the dash (above passenger footwell, close to the firewall). It is definitely fresh water (not coolant), and the only way I can imagine it getting into the ventilation system is through the cabin air intake in the cowl. My questions are: should there be some kind of drain that allows water that made its way into the intake escape? Should water be getting in there in the first place? Is there another common way exterior water can get into the ventilation system? And finally, Why does the water only pour out when I turn the blower on?

Thanks

 

The condensate drain hose on the underside of the HVAC box on the engine side of the firewall is likely clogged with leaves and debris. You probably need to get under the car to see it.

 

Thanks! Can that hose be unclogged without taking apart the heater box?

 

The rubber drain elbow comes off of the barb on the heater box. Most times you can loosen up the debris with a wire stuck in the hole. Obviously success with that method depends on how much crap is inside the heater box.

 

I never managed to find that hose, but after poking around for a while, I found two holes, one under the evaporator box, and a smaller one under the heater core. I poked a wire in each, and water began pouring out the heater core hole. I didn't see any crap get released, but hopefully that fixed the problem.
Thanks for your help.