2001 Mercedes Benz ML320 6 cyl Four Wheel Drive Automatic 119000 miles
when the temp setting is at half or less a continuos loud almost thumping noise comes from the dash. When the temp is set to above half or more (ie the heat is now coming through)speed it goes away. This is not good for living in florida!
It sounds like you have something in the blower motor cage. This happens time to time and usually either involve leaves and debree or small rodents getting caught in the " squirrel cage" potion of the blower. It will be necessary to remove the blower to get the debree out of the blower.