I have a 6530 with 120 hours on it. A recent development: the "air cleaner clogged" indicator on the main instrument panel lights up. When this first happened, (at 80 hours or so) it was persistent, so I replaced both the inner and outer air filters. This kept things quiet for awhile, but now the indicator lights up frequently again. When this happens, I pop the hood, remove the cartridge from the bracket, and tap it at the outlet end. The cartridge seems to accumulate a lot of dirt (I'm not operating in particularly dusty conditions), i.e., I can tap on the air cleaner after running the tractor for an hour or so and dust comes out of the outlet and also out of a small hole adjacent to the outlet. I've vacuumed out the cartridge carefully as well as cleaned the outer filter carefully with compressed air (followed directions in the manual). Does anyone else have this problem? I'm confident that the filter is correctly installed within the cartridge, having fiddled with it so many times now. It seems to me that this indicator is coming on too frequently, so...the cartridge not functioning correctly? Bad sensor? Something I'm missing? Any ideas and expertise much appreciated.