Gas and Oil Home Heating Furnaces - air conditioner leaking.

i have an old RUUD heat pump that is leaking water onto the air filter. i've cleaned out, as well as i can, the drip pan thing. forgive me, i'm new at this. there's alot of sludge. the drain pipe is not clogged. the unit works fine, just dripps water. by the looks of it, it started today. not that much water, but enough. could the pan be rusted through? there some rust, but not that much. the pan is directly under some fins/tubes, can the pan be removed and replaced? what else could the problem be?

thanks,
mitch.

rusted drain pan. generally would replace coil if it was old enough to lose the pan to rust. you can get a pan, however, if not from the mfr, from a sheet metal shop with proper measurements. good luck