Following related specifically to '69, but hopefully can get you going in the right direction. As a start, is the manual slide switch on top of the relay valve in the "normal" position. If it has been moved from the nomal position, the doors will stay open.
See following links as well as the attached Word document. I found it on the Internet, and I don't have the source documented, so I can't give proper credit to the originator - but it is a pretty good descriptive document:http://www.camaros.org/forum/index.php?topic=542.0http://www.camaros.org/forum/index.php?topic=626.0