Hot air under dash... FOUND!

I am fiddling with my A/C at the moment. I've always felt a gust of hot air from under the dash, and knew it had to be more than firewall heat soak (despite some good thermal image shots from another poster).

Anyway, it turns out that the hole under the dash that lets the duct from the A/C evaporator pass through into the dash vents is sealed by some sort of flexible membrane that is pop-riveted to the bulkhead. On my car the previous mouse visitors had gnawed a hole in it, but it is obviously perished, and easily crumbles when touched - might be an idea to have a look, if you're in a hot latitude and having cabin heat problems.

Thanks to my new found phone/computer skills, I can actually post a pic! (Not a very good one). Front of car to the right (RHD), gold thing is the brake booster.
Image Unavailable, Please Login

 

I note the footwell heat thread is active again, so I thought I'd bump this up. When I reinstalled the evaporator, I slipped a soft, 1" foam gasket around the upper duct, and also packed some in from above. Completely stopped the hot breeze that was blowing in over my legs.

 

No pics of that, Roberto, but it was just a square of foam rubber with a 3" hole cut out for the duct. The body of the evaporator sits nearly flush with the bulkhead, which holds it on one side, and I just experimented with packing other pieces in the hole until it sat nicely. Mad a huge difference, though. I also had the dash out and replaced the foam gasket around the three vents there, which improved efficiency a bit.