1994 Buick Lesabre hvac

[sbspence]

I've battled the hvac on this car for a couple of years now. It started with the air only blowing through the defrost and floor no panel. My trusted mechanic checked it thoroughly and found it was the "vacuum tree" under the dash and stated that no one sells a replacement and no local yards had one and even if they did they'd likely be in a similar state or soon would. My question is has anyone heard of a company rebuilding the vacuum (whatever they're called) that controls the diverting of air to the proper ducting? Mine is a low end custom with manual controls and no dual climate function. I did rig up a vacuum line through the glove box door with a golf tee for a plug. With it inserted it reverts to panel and when removed causing a vacuum dump it reverts to defrost and floor.

I wish I knew more about the inner workings of these vacuum systems I'd tinker with rebuilding them. There had to be a market for it!

I've you've heard of anyone that works on these please let me know. Thanks!

 

[pitzel]

Never heard of those units being problems, at least on the W-bodies which I'm pretty sure is the same or nearly identical hardware as on those H-Body cars. Are you sure there's no vacuum leak in the under-hood vacuum lines from which the vacuum-driven HVAC controls ultimately derive the vacuum that operates them?

Does the vacuum-driven cruise control work flawlessly? If not, that's a pretty good clue that you just need to fix a problem with the vacuum lines. The 'professional' way of doing that would involve a smoke injector, but if you carefully inspect things, particularly how the lines route around things like the battery tray, etc., you might find a discontinuity that can be repaired.

 

[alchargo]

On my '89 Bonneville I lost cruise control and the HVAC defaulted to defrost when this vacuum check valve, located up by the driver's side firewall, failed:
https://shop.advanceautoparts.com/p/acdelco-vacuum-check-valve-15-50568/15730086-P

 

[mfewtrail]

The vacuum line, check valve, or vacuum reservoir under the hood are most likely bad. Pop the hood, and look at the vacuum diagram sticker if it's still there and then locate + test each of those.