How can I safely clean this old Kenmore wall unit before summer?

You’ll usally find the model number for those old Kenmore units on a small metal data plate located just behind the front plastic grill, often near the bottom or tucked toward the side of the control knobs. To get inside, look for two screws along the bottom edge of the front panel; if there aren't any, the panel probably just snaps off with a firm tug. Once that's off, your first priority is the air filter. If it’s been sitting for years, it’s likely caked in dust and potentially brittle. Give it a good rinse in the sink with some mild dish soap and let it air dry completely before putting it back.

To clean the coils without flooding your floor, grab a vacuum with a soft brush attachment and gently go over the evaporator coils—those are the aluminum fins right behind where the filter sits. If you see mold or heavy gunk, buy a can of **no-rinse evaporator coil cleaner**. You spray the foam directly onto the fins, and as the AC runs, the condensation from the air washes the cleaner and the dirt into the drain pan and out the back. It saves you from having to use a hose inside your condo.

The real issue with these thru-the-wall units is usually the outside half. If the condenser coils on the back are plugged with dirt or spider webs, the unit will work twice as hard and blow lukewarm air. These machines are often designed to slide entirely out of thier metal "sleeve" that's built into the wall. It’s a two-person job becasue these things are heavy as lead, but sliding it out onto a sturdy table is the only way to really scrub the base pan and clear out the drainage holes properly.

Don't be intimidated by the age. These old Kenmores were built like tanks and often blow much colder than the new energy-efficient models. Just check the power cord for any cracks or brittle spots before you plug it in. If the cord looks solid, turn the dial to the coldest setting and the fan to high. If you hear the compressor kick in and it starts throwing ice-cold air, you’ve got a reliable cooler that will likely last several more seasons.

That bit about sliding it out of the wall makes me nervous. My unit is right above the baseboard heater too, and I’m worried that years of heat from the winter might have melted some of the plastic parts or the seal around the sleeve. Have you ever seen that happen?

Also, for that no-rinse foam, do I need to keep the windows open while it runs? I'm a little sensitive to smells and don't want to fill my studio with chemical fumes while it's cleaning itself out. I'm hoping it just smells like lemons or somthing.

Don't sweat the baseboard heater. Those old Kenmore sleeves are heavy-duty steel and the plastic is thick—it takes way more than a heater to melt them. One thing people miss is the fan motor. Check for small oil ports (usally yellow or red caps) on the motor housing. A few drops of 3-in-1 blue label oil can stop a squeal before it starts.

Check the drain hole at the back too. If it's plugged, condensation will back up and dump right into your heater. Use a zip tie to poke it clear. If you're sensitive to the foam spray, just crack a window for the first hour and you'll be fine.

Definitely check for mouse nests before you fire it up. I opened an old through-the-wall unit last summer and found a massive hoard of acorns and insulation jammed right against the fan. If you turn it on with all that junk in there, you'll burn out the motor or worse.

Also, grab some fresh weatherstripping foam from the hardware store. The original seal between the unit and the sleeve has probably turned to gray dust by now. Replacing that will stop the hot air from leaking back in around the edges, wich is a huge help since these old beasts already pull a ton of power.