Wandering HVAC doors - VXII single zone climate control

[TumTum]

Hi,

I've noticed the doors on my HVAC seem to wander about while I'm driving. Sometimes, with the mode set to face & floor, it changes to the windscreen and then wanders back to the original position. The display doesn't change, just the airflow. It's more obvious when I hit about 80kph, and less frequent at lower speeds. I know the doors in the HVAC can be reset on a VE, but can the VXII HVAC be reset in the same way? And does anyone have any idea wtf is going on with this anyway? It's like it's making up its own mind where the air should go...

 

[Caprice5L]

Common fault with VT/VX. Something to do with vaccuum hoses and stuff. I have the same prob, been there for nearly 3 years i reckon. Still not fixed. Dont accelerate so hard when youre doing more than 70-80kmh, and the flaps will stay put.

Theres a thin rubber hose going from the back of the engine to the firewall. Its got an inline filter looking thing on it. See if thats perished. That goes to the hvac box inside and does something with the vaccuum pressure. Thats just from what ive read on the forums in the past. If you fix it, let me know.

 

[2O4TS]

Yeah, it's a one way valve. That's where I'd start looking, from where that hose connects to the plenum. It's not holding vacuum.

If that looks all good, check to see what the vacuum is like at the vacuum reservoir on the far left side of the HVAC unit behind the glovebox.

 

[TumTum]

Found the thin end of the rubber hose under the engine cover and it was quite a loose fit. I cut off 1cm of the hose and reconnected it - feels like a better fit. Guess I'll find out tomorrow if it's sorted... will post results.

 

[TumTum]

Ok so no change yet. The one-way valve and the plenum connection looks all good now and the rubber doesn't seem perished. Looks like I'll have to have a look at the HVAC connection where the vacuum comes into the unit.