9.8 - Center Vents ( ,
Note: normally the centre vents only open when the A/C comes on.
The centre vent is vacuum controlled. The vacuum is switched by solenoids mounted under the aircon unit - either side of the trans. tunnel. Three tubes go up into the top of the dash - green for demist flaps (which are open when there is no vacuum), and black and red for the centre flap, which opens in 2 stages.
Step 1 is to check the vacuum solenoids. Earlier cars have individual solenoids, which clip onto the underside of the aircon unit. Not easy to get at, but it can be done. Later ones have a more complicated looking composite unit, which looks like it might be VERY difficult to get to and service unless the whole system is removed. Easiest place to check the vacuum is by finding the tubes to the dash top. Run engine, set air control to manual and temp to max. cold. Should have vacuum at both red and black. Turn switch to part cold, should only have vacuum at one (black?). Itís probably also a good idea to check the demist ports at this time - turn fan to demist or turn "air" switch on - should be no vacuum on green tube. Go back to normal, with "air" switch off and this should give you vacuum on the green.
Now, if the vacuum is all present and correct, culprit is likely to be the vacuum actuator buried inside the dash top. This can be tested by applying vacuum to each of the black and red tubes. They should hold vacuum, and you should be able to hear the actuator opening the flap. If there is a leak, there is little choice but to replace the actuator.
The actuator is a 2 stage affair, buried inside the dash top. The black vacuum tube plugs into the top, and opens the flap half way. This gives the gentle wafting when the system is not in full cool mode. The red tube plugs into the side, and opens stage 2, which has a membrane that should seal against the actuator rod. On mine, the sealing washer broke, allowing vacuum to leak through. A second hand unit should be reasonable cheap. Price $45 Australian.
Now to get it out and reassemble is not hard, but it needs several hours clear time. The dash top has to come out! Briefly, this is how it goes:
1. Remove under dash casings and all air ducts.
2. Remove dash side covers. One 5/16 nut at bottom, and 2 press in clips. Watch the one at the top, adjacent to the air outlet - they need gentle persuasion from the top.
3. Remove the steering wheel.
4. Remove the glovebox lid, and the electronics panel attached under the glovebox (no need to remove any components). Then remove the glovebox - gently prising the edges out of grooves either side.
5. Remove covers under light and computer switch panels and disconnect wiring harness.
6. Remove screws holding instrument cluster (4, from underneath panels removed in 5) and withdraw instrument cluster. Disconnect wiring harness as it comes forward.
7. Remove ash tray (2 screws under console lid) and gear selector trim, then remove console wood (2 nylon nuts from hole left by ashtray), and radio/heater control panel. No need to disconnect these, just pull them back.
8. Prise centre wood trim (press in clips), then remove centre vent.
9. Now you're ready to undo it all. All fasteners are easy to find. One comes up from bottom on either side, and one goes through a brace either side. There is one behind the glovebox hole, and a pair of screws angled down from just inside the opening that the vent fits into. Finally, there are two either side of the console, attached to struts.
10. Carefully, pull the dash top back from the mountings. Keep it square until it is well clear of obstruction.
11. On a clean benchtop, covered with something to protect the dash top, first remove the trim that joins the demist outlets. Undo the screws and prise the demist outlets upward. There are clips in the centre of each, and they slide under tabs at the narrow end. Remove the screws holding the centre clips.
12. Now turn it all upside down. Carefully withdraw the demist flaps.
13. Remove 2 screws on either side holding the centre flap. The actuator sits on the other side. Roll it forward, and withdraw the unit.
14. If you're this far and still sane, relax. All you have to do now is put it all back together. But:
a expect to take twice as long to reassemble as to dismantle
b admire the finesse of design of the electronics harness etc. You don't want to be here again for a long time.
c check that the rubbers on the demist flaps are properly attached.
As for the bottom damper, try the position sensor (red in colour) on the left side. The motor/gearbox is on the right. If they have to be replaced, it looks pretty easy when the dash is out of the car.