Just go to the junkyard and look at various cars, find one you like and take it, or just use some generic industrial solenoid pneumatic valve. Alternatively you could take a heater control panel from a random GM product and use that, I know for a fact the late cavalier/crapfire had an almost entirely vacuum operated heater control system with multifunction vacuum valves right on the control panel directly connected to the knobs.
For switching the vacuum source:
I'm using this in another project, but it may work for your application. 1/8" barb fitting, 12v switching, and you can get it as either a pcb mount or with pigtails. Wire a switch inline and when actuated it'll let the air pass. (you'll have to cap the line at the bottom. The switched lines are the ones on the plastic turret)
Good luck!
not vacuum operated, but Mopar used a cable operated diverter valve in the 70's and 80's that was hooked to the heater controls somehow to shut off flow thru the core while bypassing it back to the engine. otherwise put a ball valve in the "hot" hose, with a small bypass before it to allow coolant to flow thru the hoses but not thru the core..
If you want a manual solution you could use 2 of the cable operated non-bypass shut off valves.
Place one between the heater lines to be the bypass and the other between the bypass and heater core.
Other options might be checking BMWs, it looks like the 5 series may use an electronic 3 way heater control valve.
1st and 2nd gen RX7's used vacuum solenoids in the 'rat's nest'. Those are easily found and should do what you want. They have three nipples (heh heh heh he said nipples) that connect the vacuum source between two with the power off, then it seals the first one and opens the second with power on. You could set it up this way: wire the solenoid to your blower switch that way with no power it sends vacuum to the side of your valve that recirculates coolant back to the engine, then when you turn on the blower it switches vacuum to the port that opens the valve to send coolant to the heater.
The little top hat thing pops off easily so you can connect a vacuum hose.
http://m.ebay.com/itm/191250628363?nav=SEARCH
http://m.ebay.com/itm/291175452040?nav=SEARCH#
or put one of these in before the regular valve http://m.ebay.com/itm/171390423313?nav=SEARCH#
Curmudgeon wrote: 1st and 2nd gen RX7's used vacuum solenoids in the 'rat's nest'...
He ain't kidding about "rat's nest" either:
Vacuum canoe?
More vacuum canoes!
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