Well since there were no answers, I had to find out for myself. 5 10mm bolts and the glove box was out. 3 more 10mm screws and the heater motor was out. Unclip the 2 electrical connections for the underdash lights and heater power and there it was. Now the cause. Even though we have an air/pollen filter, ther is an amazing amount of ultra fine dirt and/or carbon from the electrical contacts that makes it thru. If you decide to do this, put newspaper on the floor as the dirt will require more than a vacuum. Some compressed air and a libera application of lithium grease and it is as quite as the proverial "church" .