Whistle in air conditioning (C5) - How does dash come off?

[BillCr]

I recently purchased a 3 year old C5 but I need to take the dashboard cover off to fix the aircon which issues an irritating high pitched whistle under medium fan speeds. It is not associated with the compressor as it persists when it is turned off. The whistle persists when the top vents only are open and when the bottom vents only are open so it seems to come from near the fan, probably on the interior side of the fan or the fan itself. I am desparate to take off the dashboard but cannot get a C5 manual to give me the essential clues as to how to do this. Please help anybody!! By the way - I cannot hear the noize at all, but those with good hearing (including my partner) can and say it is a very annoying high pitched whistle.

[xantia_v6]

I don't know the C5 ventilation system, but...

It initially sounds like one of the air control flaps is not sealing properly, but there should not be enough back-pressure to cause a whistle.

So I think the primary problem is likely to be that a flap is stuck in the closed position, raising the back-pressure.

If you direct the air to the upper and lower vents, and turn the fan on high, do you get copious volumes of air delivered to those vents?

Does the whistle stop if the facia vents are all opened?

On the C5, are most of the flaps controlled by cables directly from the controls (like the Xantia), or are they all controlled by servos?

[BillCr]

Thanks xantia_v6 - Plenty of air all settings. No change in sound for any vents open or shut. Only change is when fan speed 1/3 or less when sound goes away. My most urgent need is details on how I can lift the dashboard without smashing something to have a closer look and listen near the fan.

[xantia_v6]

One more idea... Have you checked that it is not a blocked pollen filter?