I'm positive that my expansion valve is not installed backwards. There's no leakage there. I actually had to install install it twice, and am now intimately familiar with those connectors... it's not fun getting at them, I had to file two wrenches to be able to turn them semi-conveniently.

I'm not really just guessing at my ACC/shutoff issues. I do have a MityVac, and I've been using it a lot. I understand how the ACC vacuum subsystem operates now. My PO had several vacuum lines disconnected, apparently in a lame attempt to have 100% recirculated air. With those reconnected, ACC is working properly. I got lucky, all 6 vacuum pods work and don't leak vacuum (yet, anyway). Unfortunately, the ACC vacuum goes off the same T on the main vacuum line as the shutoff vacuum circuit. Turns out, with the key in #2 position, the shutoff circuit is wide open to the athmosphere, so it robs the ACC circuit of all vacuum. If I disconnect the shutoff line at the T and plug that end of the T, ACC gets vacuum and works well, I get air through central and side vents in max cool mode. The problem is apparently in the vacuum kill switch on the ignition lock housing. It does the right thing (connecting IP shutoff valve to the main vacuum source) when the key is in positions #0 and #1, but when it's in the positions #2 and #3, the shutoff vacuum line (brown) is open and the IP shutoff valve apparently gets residial vacuum (I have that "can't start when warm" problem). My IP shutoff valve holds vacuum like a champ though and there's no oil in the vacuum lines. I just ran out of time yesterday and haven't finished diagnosing the kill switch. It may be malfunctioning, or perhaps the vacuum lines are switched at the ignition. I'll figure it out with time.

'81-85' SDs come with 617 engines.