Vacuum Noise from center vent.

[JJE3201999]

1999 E320 sedan. I have a vacuum noise from the center vent area. The temp control doesnt work correctly (warm all the time). Also you can hear a air leak bleed down after engine is shut down (same area). I think it could be the left center blend flap vacuum element. The compreesor is running and high side pressure gets hot to the touch, but low side is barely cool. (compressor is not cycling- dont think its low on freon)THANKS for your help! JON