Air selector from feet to face to windscreen , it changes when going up hills .

[liveline98]

Hi,

My vs colum auto ute is having trouble with the Air selector form feet to face to windscreen changes when going up hills by its self than when you are going down the hill it changes back to what I have it selected on.
I have been told to replace the selector switch in the dash.

Cheers John.

[Stugdum]

That is pretty normal, its because the switch has no electrical power whatsoever, it actually operates by redirecting vacuum from the manifold to open and close vents according to what you have selected, and when you floor it to go up a hill, the manifold vacuum drops very low, too low to keep the vents in the position you have set it to, thus the spring pressure on the vents return them to their default position temporarily until enough vacuum returns after you back off on the other side of the hill, and then the vents returns to the position you have it set to. You will also notice that if your engine is not running and you are sitting in the car with the fan going, you have no control over where the air comes out, because there is no vacuum to operate the vents. I cant remember which is the default position, I think it is down to the feet, but I could be wrong. Hope this helps.

stugdum

[hako]

You should check the vacuum reservoir which is a black plastic ball about as big as a rockmelon located under the passenger side mudguard just behind the headlight. This can crack or the hoses may perish. The idea of the reservoir is to avoid the drop in vacuum and usually it does this job well. It may also pay to trace back from the vacuum reservoir and check all vacuum lines for cracks/splits....you may even find one has fallen off.

[Brett_jjj]

Its most likely a vacuum leak somewhere.Check the vacuum lines around the engine,the vacuum reserve tank,it looks like a black plastic ball under the left front guard.Check the vac lines the that go to the purge cannister near the radiator on the drivers side.If these all check out to be ok.Then it might be a leak behind the dash.

[liveline98]

Thanks for replying, will check everything out before pulling dash apart to get to selector switch.
The car never used to have this problem?

[RX25SE]

And.....
Check the one way vacuum valve near the inlet manifold. If this is faulty, the stored vacuum will flow back into the engine under accleration.