Cyril,

Do you have the heater to the right in this picture (Air Flow)?
http://www.flickr.com/photos/advance-design_parts_co/8129448404/in/set-72157631868452754
If so here is the routing and the valve installs against the firewall with just the tubes inside the engine bay.
http://www.flickr.com/photos/advance-design_parts_co/8129334838/in/set-72157631868452754
If you have another type a picture would help.