First, check the filters and air intake screens.
If those are OK, remove the seat, and the plate that the seat is bolted to. You may find the seat plate cracked, and that would not be uncommon either. Weld it up or just replace it. I think it's about $125, IIRC. Then remove the screws that hold the top of the heater box to the bottom of the box (philips head screws IIRC). At that point, you can access the fan, the evaporator, and heater cores. It's likely that you'll find your heater core and/or evaporator core at least partially plugged, which isn't uncommon. You have to be really careful, but the evaporator can be removed with the lines attached, just far enough to get it over out of the way so you can get good access to both sides of it; and you'll want access to both sides. When you open up the box, you'll see one side-and it looks clean, once you pull it out of the box you can see the dirty side a lot better. For cleaner, I like to use a good coil cleaner-it's specifially made for the purpose and will remove 99% of the dirt, grime, mold, dog hair, back hair, and whatever else might be stuck to it. If the operator is a smoker, the core(s) will be brown, the tar makes all kinds of stuff stick to it. While you're in there, wipe out the box as best you can; and I like to remove the floor mat and insulation and clean those as well. To clean the foam insulation, spray it down with your favorite cleaner, then rinse it clean--but then hang it up to dry, in the sun with some wind works pretty good and takes a couple days to fully dry. While that's drying out, you can wipe down the interior, clean the exterior and make it like new again. Sure makes your tractor feel more like a new one. Take good care of 'er, they don't make them like that no more.
