I live near the beach. It's windy and often I get sand on the hood of my car (2000 Impreza). Just recently I noticed a drop in the fan speed inside the car. The A/C still works and I still get cold air coming out of the vents but whether the A/C is on or not the speed is greatly diminished especially in the central outlets.
Could this be due to the sand piling up somewhere in the system? I've taken the glove box out and there is no cabin air filter. I'm not sure exactly how to solve this problem.