Even I feel the purpose of that sensor is to detect sunlight. I have heard the ACC switching the blower speed to high (suddenly) whenever bright sun light falls on this sensor after driving under shadow (or moderate sunlight) for a while. I have experienced this often in the morning time. I do hear feeble rattles when driving over rough road surface. I thought it's somewhere from inside the dash. Will check this panel once. Thanks - - - Merged Post - - - How about taking a test drive to see if the noise goes away without the panel? Once confirmed, you can think of the best way to fix it.