Believe its related to heater blower. Doesnt happen all the time, When i turn blower off it goes away.
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2009 Volkswagen Jetta
Question: thumping noise coming from under passenger dash.
Answer #1patrick mannion from Greg Solow's Engine Room, February 04, 2012, 20:57Master
Probably so debris caught in the fan blades of the blower motor,we see a lot of rodents build nests in the air ducts as well particularly if the car has sat unused for a while. Remove the blower motor and inspect for debris and check the motor bearings and blades.