Thanks for the advice Brett. I am betting you are right and the rod has pulled out of the pin or I broke the pin out of the flange pulling and pushing on it. It was VERY hard to move and I followed the former owner's advice and put a handle throught rope and tied it to the knob. It was opening and closing for most of the last year with some hauling and grumbling.
Could you clarify for me the following parts of your note? At one point you write "There should be an access panel in the belly of the trailer straight across the 6-8 inches forward of the sewer outlet" Later you say I may need to "cut away part of the belly skin" . Is this cut away necessary even if there is no access panel?" How much working room is there inside the access panel for using tools?
From whom do you recommend I buy a repair kit? Are they available from places like Camping World on special order or do I need to go to a dealer or to Andy on line?
What tools do you suggest I assemble for the job? I have tin snips, sheet aluminum left over for flashing the gutters and a collection of various pliers and so forth.
Thanks again for your help. the trailer is in reach of various outlets for the average RV stuff, but I fear such products will not work on the Airstream. I found the Thetford replacement valves at Camping World, but I don't feel they will suffice.