Hey, nice effort Dave, and a very good writeup with pics. Basically a manually controlled aux air valve operated by a toggle switch under the dash, all ripe and ready for further refinements.

You're reminding me here of how much time I used to spend on my '74 140 fiddling around with its newer AAV design. It seemed every other oil change that I felt the need for an inspection, cleaning and possible readjustment to achieve a more well behaved idle. I recall I replaced it once with a new (not at all cheap then for a a young owner like me and my first new car). I was then comfortable incracking open the old one to see in detail how it worked with the internal compound bar and shutter, now playing with it to make a good spare. I had the spare adjusted high and would occasionally swap it in when the engine was going through one of its rough idle periods trying to challenge my limited auto skills and technical abilities then.

These P1800 ones were quite different in design and operation. I hadn't known about them until now, more likely I forgot what I did know. Retrofitting the later ones to your engine was not overly trivial as I soon realized when spotting that kit on Skandix.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

The AAV for a D-jet 1800/140/164 is bolted to the side of the cylinder head and it has a bulb that is exposed to coolant and works it like a coolant thermostat, but in reverse as it closes when it get hot. The 164 AAV is different, but works the same.

Starting with the K-jet/CIS 140, Volvo/Bosch used an AAV with an electric heating element.

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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

You're right, neither of those options is cheap. There was (is?) a guy selling these, rebuilt, on eBay for about $100. I got one and hot-water tested it. Can't remember why, but I sent it back and was graciously refunded. In any case, this is really a low-tech, unreliable device at best.

As Planetman noted, and my own experience with my AAV being completely disconnected has shown, the actual, practical warm-up period is not very long. Yet, should I have to leave the car outside for a protracted period in winter, I would like this option.

So, rooting around in my parts drawers I've found two items, both under $10, that I think I can combine to make a reasonable operational facsimile. One is a readily available 12V programmable digital thermostatic switch (Marlin P Jones P/N 32764-MP), the other an eBay 12V solenoid air/water valve. The T-stat device has a temperature probe that I can affix to the block and the valve would be inserted between the two existing air hoses. Using the temp switch to control the valve and playing around with its off/on temperature set points, I think I'll be able to get a good approximation of the performance of the original, lacking only the ramping function.

Will be playing around with this and report back with diagram and photos if it works. Meantime, keep those alternative suggestions coming. Always more than one way to skin a cat.