Yesterday I noticed a buzz/hum coming from my console when I turned on heater. It got much louder today and only seems to happen when I switched between the auto and manual settings. It buzzes for about 7 seconds before generating any heat, and appears to be worse when switching to the auto settting. Also, my auto setting only works after the car heats up. Otherwise, it just makes noise. Anyone know what's going on? Thanks!

 

Also, if it helps, it seems to be worse when it is colder