You can fix this by squeezing a thick bead of butyl tape on the inside of the car where the HVAC box drain penetrates the firewall. Or, you can attach some rubber tubing on the rigid tube that extends through the firewall into the engine compartment. Here's some pics of what you're dealing with.
Pull back the carpet and you should see this. The arrow points to where the bottom drain of the HVAC box extends through the firewall. Water blows back in from this point. So you have to seal this up well.
![Electrical wiring Gas Auto part Cable Wire]()
Here's what it looks like when the HVAC box is removed completely. The butyl tape really should be between the bare metal of the firewall and the front side of the circular flange you see in the first picture, above.
![Wood Gas Auto part Metal Nut]()
And here's what the whole AC box looks like. It's possible to put a piece of rubber tubing on the end of this plastic drain, but it's hard to reach. The third picture shows this box from the opposite direction, with a piece of tubing attached. If I were doing this, I'd try to find an ell-shaped piece of tubing. The drain is in the engine compartment near the power steering rack.
![Tire Automotive tire Vehicle Motor vehicle Hood]()
Pull back the carpet and you should see this. The arrow points to where the bottom drain of the HVAC box extends through the firewall. Water blows back in from this point. So you have to seal this up well.
Here's what it looks like when the HVAC box is removed completely. The butyl tape really should be between the bare metal of the firewall and the front side of the circular flange you see in the first picture, above.
And here's what the whole AC box looks like. It's possible to put a piece of rubber tubing on the end of this plastic drain, but it's hard to reach. The third picture shows this box from the opposite direction, with a piece of tubing attached. If I were doing this, I'd try to find an ell-shaped piece of tubing. The drain is in the engine compartment near the power steering rack.
