[dlphnfn]

The vents went out on the Sable (01 Vulcan) a couple months ago. Not bad when the weather is 70 degrees. Not good when it's freezing! I gotta get this done before the snow flies and I've put it off long enough.
I got under the hood today looking for and inspecting what I could find for vacuum lines. Everything "looks" good so I started it up and hovered around the engine bay. Everything sounds good. If I pull the vacuum line out of the tree (right in front of the steering wheel area) then I can hear it hissing. If I pull the elbow off where the PCV is, it chugs and almost dies. If I pull the line off the intake same thing...
My question is how do I even diagnose this thing? Knowing it's the vents vacuum "power" that's not working, am I looking for a leak in a particular place? Would it also be affecting something else? The engine runs smooth as silk and I hear no additional hissing from the engine bay.
Just looking for tips...
Erick --

 

[sheila]

Check on pass. side firewall for a vac. tee. One line going through the firewall into the dash for the hvac temp. control, other line (hose) toward pass. fender to a reserve vac. pot. Check hoses, pot and fittings for leaks and damage. Inside, under pass. kick panel, check to the left of the blower motor bottom for a white vac. plug and make sure it is plugged in securely. Next, i would remove the radio and make sure vac. plug is secure on back of temp. control knob. If all this fails, youre looking at a vac. hose leak or a faulty vac. motor (there are several) up in the dash requiring dash removal. When a hvac vac. leak occurs, all functions (modes) default to defrost. This is assuming you have manual controls. If you have the automatic (eatc), you should run the self-test before doing anything. Good luck. P.S.: That white vac. plug to the left of the blower motor bottom is on the evaporator housing just to the right of the blend door actuator motor.

 

[sheila]

Not likely, but suppose it could be temp. control knob switch.

 

[sheila]

I screwed up, wherever i said temp. control, i meant mode (function-vent, floor, defrost, ac, etc.). Temp. is controlled electrically with the blend door actuator and mode is controlled by vacuum. Sorry for the brain fart.

 

[sheila]

You can start your search at the vac. tree on drivers side firewall you were initially inspecting. That vac. junction block should be marked ac (air cond.), a/i (air intake), bb (brake booster) and s (?). Inspect the ac hose in its travel to the pass. side (connected to the cowling) to where it connects to the vac. tee i initially mentioned in my first post and go from there.

 

[dlphnfn]

Thanks Sheila. I will start with that info! Appreciate it!
Erick --

 

[thecurrent]

If you smoke or know a smoker, take the correct vacuum line off of the tree thing and blow smoke into it. Sounds like a pretty crude way to locate the leak but it should work!

 

[sheila]

Or a mech. smoke machine.

 

[sheila]

Or a cheap vac. tester from harbor freight tools.

 

[dlphnfn]

FOUND IT!! B)
It was this shiny round thing under the dash with the vacuum tube coming out the bottom of it.

I don't know what it is, but as soon as I plugged it in, the vents worked.
Thanks for the help all!
Erick --

 

[jw89sho]

That's the diverter between floor, dash, and defrost.

 

[sheila]

Glad to hear you got it fixed!