I believe that what I am working on is the defrost actuator . Its is cliped onto the top of the blower box and is operated by the blue vacuum line .My problem is the white plastic hook broke off the door. Is the hook replaceable?

 

If you can find the piece that broke off, you can probably just epoxy it back on as long as you invent a way to keep it in place while it cures. Sometimes removing the part and holding it oriented in a way where the broken plastic just sits there is the best. Other times, you can super glue the broken surfaces together and then strengthen with the epoxy. Get JB Weld at your local hardware store. We all know superglue, but it doesn't work well as an automotive fix by itself. Epoxy needs to cure overnight before trying to use the repaired part.

 

I have the piece that broke off I cant get in there to glue it and I have another junk blazer to take that piece off does it come off or do you have to replace the whole door in the blower box