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Refurbishing the HVAC vacuum selector valve in a 1978 280Z -- useful info

March 11, 201213 yr

See I have a different problem. The mode door does not operate on mine, the temp control does (my ac is inoperable at this time, another story to begin). I was thinking about using the mighty vac to test each hose to see if the dashpots were all operable.

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March 11, 201213 yr

comment_383745

IMO, the biggest problem you would have is those cheap hoses. They dry out and crack easily, and you get a vacuum leak. I had an a/c guy "replace" the leaking tube (to the fresh air door) but all he did was cut off the cracked bit from the end and put it on and say the tube was 'fixed.' It started leaking a while later, and now it's driving me nuts when I need some heat or windscreen defrosting.

What would be the proper tubing to re-do the vacuum lines? Some thick-walled silicone stuff maybe?

What about the roller thing that engages the detents on the selector when you move it? Mine was missing since I got the car. Is it actually a roller or a ball or what? I assume it's spring-loaded?

thxZ

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March 11, 201213 yr

comment_383756

IMO, the biggest problem you would have is those cheap hoses. They dry out and crack easily, and you get a vacuum leak. I had an a/c guy "replace" the leaking tube (to the fresh air door) but all he did was cut off the cracked bit from the end and put it on and say the tube was 'fixed.' It started leaking a while later, and now it's driving me nuts when I need some heat or windscreen defrosting.
What would be the proper tubing to re-do the vacuum lines? Some thick-walled silicone stuff maybe?
What about the roller thing that engages the detents on the selector when you move it? Mine was missing since I got the car. Is it actually a roller or a ball or what? I assume it's spring-loaded?
thxZ

There is, IIRC, a plastic piece that holds a spring and something like a ball bearing or a plunger. Couldn't say exactly because mine was missing the internals to the plastic piece when I opened up the dash/console to check the A/C micro switch. I'm one of those guys that throws every little odd bit and part from anything (I strip appliances, etc.) into a bucket. I found a couple of small springs and a tiny clevis pin that I shortened, rounded the end, and smoothed down the diameter of the head so as to fit into the housing- picture a very small bullet in a casinginserted into the chamber/housing followed by a spring- with just the right size of spring length to push the nose into the detent of the lever. I know, I know. I could have searched for someone parting out a car. Sometimes the MacGyver in me takes over. And it was free.

BTW, I replaced my vacuum lines with w/w tubing. I went to Grainger and poked through their stock 'till I found the right size.

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March 13, 201212 yr

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comment_383932

Sorry for being a stranger...

Grant, yes, I used silicone dielectric grease. I'm just used to calling it "vacuum grease," from my laboratory days. As far as I can tell, it's the same stuff.

Tomo, I'm remembering the detent the same way as Willoughby, but it's been a long time.