Evaporative coolers, also sometimes called swamp coolers, are an alternative to traditional air conditioning systems that make use of cold water vapor being evaporated into your home's air to bring down the temperature. Just like regular air conditioners, however, they need to be properly prepared for the winter months to prevent any damage to their intricate and fragile inner machinery so that you'll be able to enjoy cool air in your home when the summer months finally roll around again.
What You'll Need
You'll need a clean sponge, a pair of gloves, a tarp or cover, a shop vacuum, replacement evaporative pads, a batt of insulation and a piece of plywood that are both large enough to cover your evaporative cooler vent. All of these items can be found at most hardware stores if you don't already have them at home.
Winterizing an Evaporative Cooler
The first and most important thing that you have to do when preparing your evaporative cooler for winter is to disconnect the water line from the unit itself. You can do this by turning off the water supply to the unit itself (usually located inside, at the start of the pipe that carries water to the cooler) and then unscrewing the water supply line from the cooler itself (turning counter-clockwise).
Next, you'll want to drain any remaining water from inside the cooler. Do this by removing the plug at the bottom of the cooler's drain pan (some plugs are pulled straight out, others are unscrewed).
Next, use the shop vacuum to remove any scum, dirt, and other contaminants which may have become stuck on the interior of the drain pan.
Finally, to ensure that the pan is completely dry and clean, you should use a new sponge to wipe down the entirety of the drain pan, wringing out the water as you go.
Next, you'll want to open up the casing for the evaporative pads (usually located on the side of the unit and can be unclasped by hand) and replace the old pads with fresh new ones. This will help prevent mold and mildew growth over the summer and prevent odors from taking root in the unit.
Then, you'll want to cover the evaporative cooler itself. You can use a tarp, but hardware stores sell specialized evaporative cooler covers which tie down on the sides and provide a greater degree of protection from the elements (and often breath better than tarps, prevent moisture from causing rust and corrosion to the unit).
Finally, on the interior of your house, you'll want to cover the evaporative cooler vent with a piece of insulation cut to fit the vent and a piece of plywood over the top of it. Depending on the size of the vent, you may need to cut the insulation and plywood to size, which can be done with a utility knife (for insulation) and a table saw (for plywood). This helps prevent heat loss throughout the winter and can help cut down on your energy bills.
If you need more help, talk with a local HVAC contractor.