Swamp Cooler Maintenance: A Spring Start-Up and Fall Shutdown Checklist

A swamp cooler needs two service visits a year: one in spring before you turn it on, and one in fall before the water line can freeze. This checklist covers both, plus the quick checks in between, using guidance from a national lab and the owner's manuals cooler makers publish.

Updated October 28, 2026

The short version

Service the cooler at spring start-up and again at fall shutdown, and look it over every couple of months while it runs.
Cut power at the disconnect before you open the cabinet. A thermostat doesn't count, because it can start the cooler while you work.
Settings like belt tension and the pan's water level vary by model, so check your own manual before adjusting them.
Drain the pan whenever the cooler will sit idle for more than a few days, and drain the water line before it freezes.

Before you start

Shut off power to the cooler before you open it. Phoenix Manufacturing's manual for its AeroCool coolers says it can take more than one disconnect to de-energize everything, and that a thermostat must never stand in for a disconnect because it can reset and start the cooler unexpectedly. That includes a cooler run by a smart thermostat. Switch off the service disconnect and lock it, or tag it if it won't lock, and don't run the cooler with its access panels off, which can overload the blower motor (AeroCool manual).

Find the model number on the cooler's nameplate and get the owner's manual for that model. Makers give different numbers for the same jobs, as the table below shows, and yours is the one to follow. Cooler work often happens on a roof, so plan for safe footing too.

Spring start-up

PNNL's spring list is short: clean or replace the pads, check the belt tension and look the cabinet over for damage (PNNL). Work through it before the first hot week, while there's still time to order pads or a belt.

1Remove the cover and open the dampers. Take off the winter cover and reopen any dampers you closed in the fall, at the ceiling vents and in the cooler duct. Some ceiling vents have barometric dampers that open on their own when the cooler runs (PNNL).
2Turn the moving parts by hand. Before the first run of the season, spin the blower wheel and the motor and pump shafts by hand to make sure they turn freely. Phoenix warns that skipping this can burn out a motor (AeroCool manual).
3Clean the pan and the pump. Wipe scale and dirt out of the pan with warm water, a soft cloth and mild detergent. Skip wire brushes, and don't hose down the cabinet: water can get into the motor and pump or run into the ductwork (AeroCool manual). Champion says the pump needs a cleaning once a year at start-up. Take off its base, clean it and check that the impeller spins freely (Champion manual).
4Check the pads and the water distribution. Replace pads that are torn, worn or mildewed (PNNL). Champion says its aspen pads should be replaced once or twice a season (Champion manual). For rigid media, Phoenix says to hose off the side that faces outdoors and brush scale off the inlet edges with a stiff bristle brush, never a wire one. Use the pad type your cooler was built for: Phoenix says aspen or other pads won't work in its rigid-media coolers and will void the warranty (AeroCool manual). Then clear the distribution holes or nozzles; PNNL suggests vinegar to dissolve mineral buildup (PNNL).
5Oil the bearings, lightly. If the blower shaft bearings have oil cups, add the non-detergent oil your manual names; the table below compares three. Champion says motors with no oil ports are oiled for life at the factory, and that too much oil can reach the motor windings and burn the motor out (Champion manual).
6Set the belt tension. Squeeze the belt to check it. Phoenix's manuals call for ½ to ¾ inch of give, and Champion's for ¾ inch under 3 pounds of force. Adjust it by moving the motor on its bracket, never by changing the motor pulley, and replace a belt that shows fraying or cracks (AeroCool manual, Champion manual).
7Reconnect the water and set the float. Turn the water on and check the line and fittings for leaks. Bend the float rod until the pan fills to the level in your manual: 2½ inches deep in Phoenix's coolers, within an inch of the top of the pan in Champion's. Make sure the drain line goes to a proper drain and not onto the roof, where minerals can build up and damage it, and that the bleed-off line isn't clogged (AeroCool manual, Champion manual). Both of those manuals also say not to connect a cooler to softened water, which speeds corrosion.
8Test it, pump first. Run the pump alone until every pad is evenly wet, with no dry streaks. Then open windows or relief vents, start the blower and try each speed. Giving the pump a few minutes' head start keeps the first rush of air from coming in warm (AeroCool manual).

On a rotary wall switch, that pre-wet is up to you every time you turn the cooler on. A controller or thermostat adapter that starts the pump before the blower handles it automatically; our guide to smart thermostats for swamp coolers covers the options.

Where cooler manuals differ

The table compares three owner's manuals: Champion's for its aspen-pad down-draft and side-draft coolers, and Phoenix's for its Frigiking (aspen) and AeroCool (rigid media) lines. If your manual says something else, go with yours.

Maintenance intervals and settings from three swamp cooler owner's manuals
	Champion (aspen)	Phoenix Frigiking (aspen)	Phoenix AeroCool (rigid)
Full service	Spring start-up and winter shutdown	At least once a year	At least once a year, with an inspection every 2 months in use
Pads	Replace once or twice a season	Replace at the yearly service	Check yearly; clean or replace
Bearing oil	A few drops of non-detergent 20/30 weight, once a year	SAE 30 non-detergent in the oil cups	SAE 20W or 30W non-detergent; check 20 to 30 days after start-up, then about every 3 months of use
Belt give	¾ inch under 3 lb of force	½ to ¾ inch	½ to ¾ inch
Water level	Within 1 inch of the top of the pan	2½ inches deep	2½ inches deep
Chemical treatments	Damage not covered by warranty	Void the warranty	Void the warranty

During the cooling season

Phoenix suggests opening the cooler for a look every two months while it's in use. Check for leaks, dry spots or streaks on the pads, loose bolts and set screws, bearing noise, a blower wheel that drags, the float level, dirty water in the pan, and belt wear and tension (AeroCool manual). With aspen pads, Champion recommends a fresh set at mid-season, since a clean pad soaks up more water and puts out more cool air (Champion manual).

Drain the pan whenever the cooler will sit unused for more than a few days. Standing water can breed mosquitoes and bacteria, including Legionella, which causes Legionnaires' disease (PNNL). If the cooler smells musty, Champion's troubleshooting chart points to stale water, mildewed or clogged pads, or pads that aren't wetting properly. The fixes are to drain and clean the pan, replace the pads and clear the water distribution (Champion manual).

Hard water leaves scale on the pads and in the pan. A bleed-off line slows the buildup by sending a little pan water down the drain, but it can raise water use by 10% to 50%. An auto-flush (dump pump) that empties and refills the pan every 8 to 12 hours of running uses less water (PNNL). Champion suggests starting a bleed-off at 1 to 2 gallons an hour and increasing it if needed (Champion manual).

Fall shutdown

Do this at the end of the season, before the first freeze.

1Turn off the power. Switch off the disconnect. Phoenix says to disconnect power for long periods of non-use, and Champion says to unplug the motor and pump inside the cooler (AeroCool manual, Champion manual).
2Shut off and drain the water line. Close the supply valve, drain the line and leave it disconnected at both the cooler and the supply, so no water is left in it to freeze (AeroCool manual, Champion manual).
3Drain and clean the pan. Pull the overflow standpipe and drain the pan to a proper drain, not onto the roof (AeroCool manual). Clean off mineral deposits, especially on moving parts, fan joints, spray nozzles and the pan, and let the whole unit dry out (PNNL).
4Close the dampers. Close the ceiling vent dampers and any damper in a ducted cooler's supply. PNNL says to keep them closed through the heating season (PNNL); an open one lets heated air leak out through the cooler duct.
5Cover the cooler. A plastic or canvas cover over the whole unit keeps dirt and dust out over the winter (PNNL), and Champion suggests one to protect the finish (Champion manual).

A window cooler should come out of the window and go into storage so the window can close for winter (PNNL).

If getting onto the roof isn't safe for you, ask about help. The City of Albuquerque offers free evaporative cooler start-up and shut-down service in spring and fall to Albuquerque and Bernalillo County residents 60 and older. Call the Senior Information Line at 505-764-6400 to find out when requests open (City of Albuquerque).