BMW Repair: the clicking nosie from my vent, coolant leaks, center vent

Question
hello, my ride is 2000 E46. when i turn on my heater, some annoying clicking noise always come from the vent (especially from the center vent on the dash board) when i shift the speed high or low the noise comes out again, and stopped after few mins or stopped randomly. Moreover, when i make a acceleration the noise comes out again. i don't know how come? ~~does the chilly weather effect(mostly under -20¡ãC in the winter)? or any part i need to replace and how to replace them? such as blower motor? Motor Resistor?
Please help me  
thanks
regards  

Answer
Simriy, The only thing I know of is an A/C hose making humming/vibration noises through the center. This maybe possible if the A/C compressor is running for defrost reasons. There is an updated A/C hose with a vibration silencer to eliminate noises. There is a service bulletin on the subject. I can't hear your noise so I don't know if this is what you're experiencing. Make sure you don't have any coolant leaks that might be letting air into the heater core. Top off fluid if needed.
-Evan