The Parts of an Evaporative Cooler (Swamp Cooler)

Illustration showing the parts of an evaporative cooler

The Spruce / Mira Norian

Evaporative coolers, often known as swamp coolers, work by extremely simple physics: As water evaporates, it effectively "consumes" heat from the surrounding air. It is the same principle by which an air fan cools you as it evaporates perspiration from your skin. The parts of an evaporative cooler are all designed to facilitate efficient evaporation of water and circulation of the cooled air into the home.

Knowing about the various parts of the appliance can make it easier to maintain and repair your cooler. Here is a rundown of the anatomy of an evaporative cooler. Some parts may need to be replaced often, while others may last the full life of the appliance.


Evaporative cooler motors are relatively small in size, usually ranging from 1/3 to 1 horsepower. Most operate on 115/120 volts of power, which is the reason they use relatively little electricity when compared to 240-volt central air conditioning systems. The motors on evaporative coolers usually work fine until they don't—they don't gradually decline. If you are changing the motor in an evaporative cooler, make sure you examine the current motor to see what size it is and how many speeds it has.

Changing the motor on a cooler is not a difficult project, but it does require some basic electrical know-how to connect the wires. Don't try this unless you are confident in those skills. 

Swamp cooler motor
Aaron Stickley / The Spruce

Shaft Bearings

The bearings are the small round metal spheres that allow the drive shaft on the blower to spin smoothly when driven by the motor. Depending on the appliance model, the bearings come in either high-rise and low-rise bearing assemblies, and the bore (diameter) of the bearings are usually either 3/4 or 1 inch.

The blower shaft spins constantly on the bearings, so if the bearings are going bad, the appliance often makes a piercing, squeaking sound. Sometimes this sound can be remedied by lubricating the bearings. If that doesn’t work, the bearings will need to be replaced. If you have any doubts about which kind you have, bring the old bearings along when buying the replacements.

To access the bearings for lubrication or replacement, you will need to disassemble the drive shaft. Again, this is a job possible for a skilled DIYer, but don't tackle it if you're not confident. 

Motor Pulley

An evaporative cooler has one pulley at each end of the drive belt: the motor pulley and the blower pulley. The pulleys rarely go bad, but if necessary they can be removed by loosening the Allen screws that hold them in place. The replacement pulleys should match the size and type indicated by the manufacturer of your cooler. Using a different-sized pulley could put unnecessary stress on the motor and affect how the cooler runs.

It is a good idea to check the motor pulley periodically for dents and alignment. It sits on the motor shaft and is fastened in place with an Allen screw. Motor pulleys come in different sizes for different-sized motors. When replacing the motor pulley with an adjustable one, be sure to set the adjustment to the motor specific size.

Swamp cooler motor pulley
Aaron Stickley / The Spruce

Blower Pulley

The other pulley found in an evaporative cooler is the blower pulley, which is positioned lower on the unit, in line with the blower shaft. As with the motor pulley, the blower pulley must be the correct size to ensure that the swamp cooler works correctly. When replacing a blower pulley, make sure to match the pulley to the unit, so that the blower can move enough air to cool effectively. 

Swamp cooler blower pulley
Aaron Stickley / The Spruce


The V-belt is a long-lasting type of drive belt. Its design makes for minimal slippage in the pulleys and it is easy on the bearings, making it a good choice for evaporative coolers. The V-belt can stretch and become loose in the pulleys, however, and it eventually wears out. And the V-belt must be aligned straight to work effectively.

When inspecting the V-belt, check the pulley positioning and adjust as necessary so that the pulleys are correctly aligned for straight movement of the belt. Also check the V-belt tension, making sure it matches the manufacturer's recommendations. 

V-belts come in a variety of sizes, so if you are replacing one, take care to choose the right size. If the belt is beginning to crack, it may be a good idea to replace it before it breaks.

Swamp cooler v-belt
Aaron Stickley / The Spruce

Water Pump

The water pump in an evaporative cooler brings the water from the pan to the distribution tubing, and from there onto the pads. The evaporation of water from the pads is what allows the appliance to cool the air, so if the pads are not being saturated with water, the pump may need to be replaced. If the pump is operating correctly but does not keep the cooler pads wet enough, you may want to upsize the pump to a larger one that can move more water.

Drain and Overflow Tube

The drain is a hollow tube that is mounted in the bottom of the cooler pan. It can be removed to drain the water out of the cooler pan, and it also acts as an overflow to allow excess water to drain out if the float is allowing the pan to fill too high. Excess water will go up and over the drain tube and spill onto the ground, alerting you to the fact that there is a problem.

Float Valve

The float valve sits in the cooler pan and regulates the height of the water. It works in much the same way as the float ball or float cup in a toilet tank. The float valve rises and falls with the water level and its lever shuts off the water supply when the water in the pan reaches the required level. The water level must be high enough so that the pump can draw water up to the evaporative pads, but not so high that the water flows into the overflow tube. Adjusting the water to the right height is usually just a matter of manually bending the float rod until the water shuts off at the proper level

A float valve that doesn’t turn the water off correctly is a common problem, but it is a part that is easy to replace. You can replace a float valve in a few minutes with parts that cost just a few dollars.

Swamp cooler float valve
Aaron Stickley / The Spruce

Evaporative Pads

The pads are where the air cooling occurs, as water delivered to the pads by the water pump evaporates under the air blown through the pads by the cooler motor. Pads for evaporative coolers come in many types, including foamed polyester, slit expanded paper, and wood strips. The most common and cheapest cooler pads are the ones made from wood strips. These pads work well, but if the strips get loose, they can clog up the pump, so placing an extra screen around the pump can be a good idea.

Evaporative pads also come in a variety of sizes, so take measurements of the inside of the cooler panels when buying new pads. Cooler pads should be changed each year, either when you winterize or de-winterize the cooler.

Swamp cooler pads
Aaron Stickley / The Spruce

Distribution Tubing

The distribution tubing, commonly called the spider, distributes the water from the pump to the cooler pads. The tubing can sometimes get clogged, and it may require cleaning or even replacement if you're not getting enough water out of it. It is a good idea to check the distribution tubing regularly, especially if the air doesn’t seem cool enough.

Swamp cooler distribution tubing
Aaron Stickley / The Spruce

Wire Connection Box

The wire connection box is where the main power supply comes into the cooler. The incoming power supply is connected to a wire connection block, where individual wire leads feed power to the blower motor, water pump, and any other powered features in the cooler. 

There normally is not much repair needed at the wire connection box, except possibly to check the wiring connections and tighten any loose ones.