Hi, hope someone can help...

My 2010 L322 4.4 TDV8 Climate Control isn't working as expected. In full auto mode, and set to 21 degrees on both sides, it seems to sometimes get to temperature, other times go too hot and make the cabin really stuffy. It seems to work better, if you set it to blow to feet, face and windscreen, or indeed if you alter the blower speed, but left on full auto, it's all over the place. I was under the impression you just set the temp and it keeps you at that temperature come rain or shine, but instead, I'm having to constantly change the settings. It is fully gassed.

There is a whistle that comes and goes from inside the dash in front of the driver as if something is in the vent stopping a flap opening or closing, but that doesn't feel like the whole cause.

Any ideas?