My vent fan suddenly started making a "ticking" noise correlated to the speed setting. This became a "thumping" noise as I dialed up the fan speed. I had previously been able to change the filter under the glove box myself, and I decided to start there. The filter was remarkably clean and showed no signs of chafe or abrasion. I further reached up into the space. There are cables and other things there which I could not see. I was expecting some trash or leaves. Suddenly I felt something soft deep in the recess and pulled out a recently dead mouse. Both the noise and the mouse are gone!