auto dim side mirror dead, common?

[jhg41977]

I got in the Cayenne last night for a quick trip to Lowes. I noticed I was nearly blind from the headlights on the car behind me. Odd, I thought this had auto dim mirrors (Ive only had it a month). Yup the rear view and passenger sides are dark and the drivers is not.

Is this a common issue? How do I determine if it is a bad glass or something else?

2008 Cayenne GTS