The previous owner had central ac installed upstairs, but for the downstairs, we only have a window/wall unit. It actually sits in what was formerly a window, but has been "build in" to hold the unit.

My problem is, last year it started to get that funky moldy/mildew smell. Well this year, after running it for a few days (it's crazy hot here) the smell has returned with a vengence. It also sometimes spits little black specs or crap out.

It's old and loud, but it works real well to cool the downstairs. We really just don't have the cash to buy a new one right now if we don't have to.

What can be done to clean/maintain this thing? I've read so far to possibly hose out the back. The filter has been cleaned real well, but how can I clean the coils on the inside? Is there a special spray I can get, or any solutions I can make up on my own? I sprayed it with lysol and all that does is make it smell like mildew and lysol.

Pulling it out isn't an option, as my house is raised. From the outside, the unit sits about 9' from the ground. Though I also read that it might be in a housing, mounted to where it was installed, and I can just pull the "guts" out from the inside, and hose the whole works down.

Another question...is it normal for there to be no water drain on the outside? I ask because I worry a bit that it may be draining into my wall? Don't they need to get rid of condensation etc, like my cental ac? Or do some models just not need to drain?

Yes.... The air conditioner needs to drain away the condensation. The unit also needs to be at a slight angle so the water runs toward the back.

Sometimes the drain holes in the back of the metal housing can become clogged.

You should be able to pull the unit out of the housing from the inside. You actually need to do that in order to make sure the unit housing is clean and the drain holes are clear and not clogged.

a little bleach in the pan helps keep the funky smell away too....

just a tiny amount will kill the creepy crawlies.

Also make sure your evap coil is clean and you keep the filter clean, as well as the condenser coil. And as said above, make sure the weep holes are clear, they are usually in the bottom.

Another trouble area is the slingers on the fan blade, if you grow fungus on them,(They actually go into the water and sling it on the condenser coil) it unbalances the blade and will make noise.

And before anyone gives you any crap, window units are by far the most efficient air conditioning system.

You can get cans of coil cleaning foam spray at home depot