nonopening intake vent for interior heating/cooling system

[teigan]

i removed the vent shroud inside the bonnet today to replace some disintegrating foam seals. since everything was open, i decided to test out the system. i was alarmed to find out the main intake vent below the windscreen shuts once the car gets vacuum, and doesn't open again no matter what position the climate controls are at. the actuator doesn't open the vent again until the engine is shut down. there's also a 3"x4" rectangular hole taped up (presumably by lotus) that serves no useful purpose. can somebody explain any of these mysteries?

[cnh1990]

The vent is controled by an air valve. The air valve has a plunger that when pressed in allows vaccum through it to move the actuator of the vent flap. The air valve sits in a saddle clamp 1/2 way behind the glove and the radio pod in US Fed cars. The plunger of the air valve is operated by rotary cams connected to knobs of the heater controls. If the air valve has shifted in the saddle clamp or if the spring loaded air valve is broken(broken spring)the plunger will not rise when the cam rotates and lessens pressure on the plunger tip. In either case if it allows constant vaccum to the flap actuator it will close it as soon as the car is turned on. There is an easy way to gain access to the air valves if it is required by dropping the glove box liner out the bottm to get working room for the oontrols. Much easier than taking apartthe radio pod.

If you need more in depth instructions I can supply that as well.
Good Luck

Calvin

[teigan]

thanks calvin. i'll have to take it apart again and examine all you mention. i remember the spring works, but something else is obviously wonky.

[fflyingdog]

HI Calvin
Do you of an easy(ish) way of gaining access to the actuator its self? as my fresh air flap sits permanently open,all vac pipes hooked up correctly i think the diaphram may have torn so i need to replace the actual actuator.
Cheers
Nick s4s

Edited by fflyingdog on Saturday 9th December 23:16

[cnh1990]

Nick,
I have never had to access the actual actuator before. It would be very unusal for that to fail as in I have never seen a bad one. I suppose it is possible. But if the actuator diaphram was torn/leaking and the controls activated I would think there would be some sort of an air leak that would cause the other set of internal flap divertors to not work as well due to not enough vacumm. Not sure if the newer S body cars as the S4s have the same items as the the older models. If they do that air valve has been a constant failure issue. In many cases it may not be broken but has slipped down in the saddle clamp due to the cam pressure as it rotates. If it slips even a 1/16th of inch in the clamp it will cause a malfunction. In one case the very tiny plastic cap on the plunger fell off that caused the problem.

Check the valve 1st. With vacumm on access the air valve plunger, use a small flat blade screwdriver or your finger nail to press down on plunger and have another person see if the flap moves. Many times one can hear it open and close. If the flap works by pressing down on the plunger but not by the cam the valve must be moved slightly in the clamp. It is a balancing act to center the valve. When I was doing mine I snapped the very small sipgot off and a new valve cost me $35 for the small part.

The only problem I can see is that it might be more difficult to access he air vavles in RHD cars becasue it is somewhat to the right of the radio pod in US Fed cars.

Edited by cnh1990 on Monday 11th December 16:25

Edited by cnh1990 on Monday 11th December 16:29

[fflyingdog]

Thanks alot i shall check that when i get home in a couple weeks,because you see whats really odd is that if i select the fresh air 'in' setting and actually push the flap down it will stay down but just wont do it under a head of steam from the dial knob so you may be right and the plunger isnt being pushed far enough ,thanks again for the info.
Cheers
Nick

[cnh1990]

I have seen that exact thing happen, it was this little white plastic tip that got worn down a bit. The tip sat on the metal rod of the plunger and was the contact point with the cam lobe. it wore down or was pushed down on rodjust enough to give partial vacumm to the actuator. With the control in the proper position the plunger was only partially depressed not supplying enough vacumm to trigger the actuator until we pressed the plunger manually. We adjusted the valve as it was more presise. I have others but a bit of material or glue under the white plastic tip and the rod to build it up little. I think that is the harder of the two to do.