HVAC Question

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SteveLNew

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Kansas City
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Steve
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1986 GMC
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K1500
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5.7 LS1
I have searched through the threads and haven't found anything in this forum, so excuse me if this has been posted someone where prior.

Is it necessary to have the vacuum canister to run the HVAC system or can I just hook it up straight to a vacuum source off the intake?

Also why is this so hard to find? Can someone point me in the right direction?
If my truck doesn't currently have AC is it even necessary?

Thanks

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AuroraGirl

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Taylor
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1978, 1980
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K10, K25
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400(?), 350
I have searched through the threads and haven't found anything in this forum, so excuse me if this has been posted someone where prior.

Is it necessary to have the vacuum canister to run the HVAC system or can I just hook it up straight to a vacuum source off the intake?

Also why is this so hard to find? Can someone point me in the right direction?
If my truck doesn't currently have AC is it even necessary?

Thanks

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when you run low on vacuum your system no longer is pulling the things like it was or whatever so the position of a door may change and also theh controls that require vac to move would be very ineffective unless under idle, or a good coast id think. so youd have to time movements to that assuming it doesnt like play with your actuators in real time
 

Craig 85

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1985
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K30 SRW
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454/TH-400/NP205
Aurora girl is correct. If you punch the accelerator, you will lose vacuum in the system and the blend doors will open or close due to the loss of vacuum. The black ball by the brake booster is a reservoir to prevent that.

The part you have circled would have to come from a junk yard. They can get pretty brittle.

Here's some of the diagrams I have saved over the years. In the third diagram, disregard the upper left part of the diagram, it's for a fuel injected engine.

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wlwarnke

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Mine was missing this canister so I made one out of a stainless float (similar to a toilet tank float) from the scrap bin at work. Welded a hose barb on it, and got a check valve Tee fitting from Vatozone. It worked beautifully. I could hold full throttle as long as needed/wanted and the air kept coming out of the dash vents.
 

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