Have you looked at how it shuts off the defrost and how it opens etc.? My plenum looks to be untouched but no matter where you set the defrost it leaves a big hole open to the floor on rh side of tunnel. Thanks for you input alex........if these are all that way I am going to do sometin with this sucker! All the humidity in the pacific nw it would have to idle in the drive way for 2 hrs before I could drive it to work! I couldnt imagine what would happen if it frosted.