1968 plymouth valiant 100 a/c vacuum diagram (factory installed) with 225 slant 6

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There were many part numbers applied to those 5-button switches, and they interchange. Whichever one you have bought will work in your car once you sort out the vacuum hose routing correctly. The diagram you need is in the FSM, chapter 24. Your type of factory air system was used from '65-'72. The heater water valve through '70 had two vacuum hoses going to it: one to open the valve and one to close it. The water valve for '71 and '72 had one vacuum hose; it was spring-loaded rather than having the "other side" vacuum hose. This didn't (and doesn't) necessitate a different switch, just different hose configurations. Once you go through, hose by hose, and make sure vacuum goes (and doesn't go) to where it should (and shouldn't) be in every button position, your system will work correctly. It's tedious to figure out, and while you're in the middle of it it seems like it'll never work correctly, but keep at it, and it will.
 
slantsixdan said:
There were many part numbers applied to those 5-button switches, and they interchange. Whichever one you have bought will work in your car once you sort out the vacuum hose routing correctly. The diagram you need is in the FSM, chapter 24. Your type of factory air system was used from '65-'72. The heater water valve through '70 had two vacuum hoses going to it: one to open the valve and one to close it. The water valve for '71 and '72 had one vacuum hose; it was spring-loaded rather than having the "other side" vacuum hose. This didn't (and doesn't) necessitate a different switch, just different hose configurations. Once you go through, hose by hose, and make sure vacuum goes (and doesn't go) to where it should (and shouldn't) be in every button position, your system will work correctly. It's tedious to figure out, and while you're in the middle of it it seems like it'll never work correctly, but keep at it, and it will.
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THANK YOU SO MUCH !!! I have been going crazy trying to get everything working correctly
 
Glad to help out. I mention the heater water valve because the pre-'71 type has been unavailable for years, or very expensive when you can find one, so often the earlier cars have been repaired somewhen along the line with a later-type (single vacuum hose) valve -- this, by the way, is a repair I'm completely onside with. Anyhow, if you find a single-hose valve, you'll have to deviate from the factory vacuum diagram to get everything working right.
 
slantsixdan said:
Glad to help out. I mention the heater water valve because the pre-'71 type has been unavailable for years, or very expensive when you can find one, so often the earlier cars have been repaired somewhen along the line with a later-type (single vacuum hose) valve -- this, by the way, is a repair I'm completely onside with. Anyhow, if you find a single-hose valve, you'll have to deviate from the factory vacuum diagram to get everything working right.
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Dan, does anyone repop the later style valve?
 
Use this one for cars with 5/8" heater hose, or this one for cars with 1/2" heater hose. Most of the '70-'72 cars have 1/2" on the inlet side of the heater; pre-'70 and post-'72 cars mostly have 5/8".
 
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slantsixdan said:
Use this one for cars with 5/8" heater hose, or this one for cars with 1/2" heater hose. Most of the '70-'72 cars have 1/2" on the inlet side of the heater; pre-'70 and post-'72 cars mostly have 5/8""] for cars with 1/2" heater hose. Most of the '70-'72 cars have 1/2" on the inlet side of the heater; pre-'70 and post-'72 cars mostly have 5/8"
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Thank you Dan. Any idea how much vacuum it takes to open the valve?
 
Not a whole lot; it's easy to do with just mouth suction. If you're using a spring-loaded heater valve you'll want to have a vacuum reservoir with check valve. The factory item is the black plastic thing in the pic here (you can see the original '71-up heater valve next to it -- looks a little different to the ones I linked). If you can't find one of those, this similar one will be fine. I like to also run a secondary check valve, genuine Chrysler part. The reason why you put check valves is so if you're roaring up a hill, accelerator mashed to the floorboard, near-zero manifold vacuum, your controls still work and all your mode doors and the heater valve stay where you tell them to go.
 
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