Dash Whine

[weiln12]

OK Guys, got a question I can't find an answer to after searching.

My dash has a very annoying whine coming from the dash. Here are some descriptions and symptoms:
-it's sounds deeper in the dash, like back under the windshield vents
-it does not change frequency with fan speed or vehicle speed
-it stops as soon as I turn off the HVAC
-it only does it while the OUTSIDE temperature is cold (<~35*-40* F), it stops when it warms up OUTSIDE and starts when it gets cold OUTSIDE, including on long trips where the temperature changes
-it goes away when I turn left, and gets louder when I turn right

This past weekend I cleaned and lubed the HVAC sampling fan. No real change. The whine sounds deeper in the dash than the HVAC control though, so I wasn't pinning my hopes on this fixing it.

It doesn't sound like a blower motor since the frequency doesn't change with fan speed. Is there an external sampling fan or something?