Walt You probably have some leaves turning into mulch in the bottom of your A/C box. Leaves fall throught the screen over the cowl and decompose in the bottom of the air box. It's a bear to clean out, as with the fan removed you can *just* get your hand bent around to touch the muck. I used a wet/dry vac with a length of heater hose attached to get the stuff from the blower side, then blew air back into the drain hose from the other side. Eventually, you can get most of it out. Mike [duplicate quote snipped by moderator]