It has annoyed me that rear vents are such a hard mod to do because of the air box. The standard one is obviously designed for it because it has the output molded on but I have always thought it is probably just blanked off with a bit of plastic inside!! Simple to remove if you can get in there to find out what/where.
Tonight I have put an endoscope camera up the air box (Doing it in the dark helped me keep track of where the camera was by watching the light through the white plastic!). First I put it up the hole where the ducting to the rear vents would go. It basically goes up the front of the air box to the top. At the top there is a brace going across the duct which has a screw that you can get to behind the radio. (Just about it is behind the radio frame)
It is my belief that this brace holds a blank in place across the top of the air box. I removed the screw (dropping the screw down the back of the radio - oops!) and nothing appeared to move however I now have a tiny flow out of the hole where I had none before. I think this really did hold the blank in place and without a screw mine is now loose allowing a dribble of air...
I then put the camera in through the top by removing the centre vents. I can get right into the box this way and have a basic layout in my head now.
I believe the way the rear heater vents are blanked off is via a panel between the top of the air box held by the screw I mentioned earlier and that it could easily be removed through the top if the dash were out.
I am going to drill a small hole in my air box (that I can easily plug up) when I get chance to confirm this. It will only be in the rear vents duct so if I cannot get the rear vents unblocked no air will escape anyway!
Anyway the reason for me posting is I was hoping members might confirm something for me. First from looking at the air box I believe the rear vents operate when the four dash vents do. Is that correct???
Secondly does anyone have a picture showing the top of the airbox with the dash removed. (e.g when doing an airbag or something???) Any help would be brillant.
Here are two pictures from inside, the first from the bottom up the rear duct, the second from the top showing the flap that stops the dash vents working....
Any help would be much appreciated....