What causes the motor to shut down and overheat and then come back on after cooling down?

If motor sheave is not properly adjusted the motor will overheat and shut off until it cools down.

On all window and mobile models, operating the unit without front discharge grill in place will cause the motor to over heat and shut off until it cools down.

Step 1 - Remove Side Wall Cover or Pad Frame (Louver)

To access the internal components of your swamp cooler including your swamp cooler motor you must simply remove the screws from the back side panel or slide the pad frame up and out of the swamp cooler. Once the screws are removed or pad frame lifted out you should easily be able to slide out the back panel or pad frame to expose interior components.

Step 2 - Check Belt Tension

The sides of your swamp cooler sill slide off very easily and doing this will expose the water pump, motor and belted fan inside. Once inside check the tension of the belt running from the swamp cooler motor to the fan. It should not be too tight or too lose. Incorrect fan belt tension could cause your swamp cooler motor to overheat. Roughly speaking there should be about 1 inch of play in the tension of your fan belt.  You can adjust this by using an Allen wrench and adjusting the motor pulley (sheave).

Step 3 - Check Shaft Bearings

Your motor will have two shaft bearings that are sometimes called "squirrel cage" shaft bearings. Each of these shaft bearings should have an oil port attached. Make sure that these shaft bearings have enough oil to spin freely. If these bearings do not have enough oil they can begin to seize and cause the swamp cooler motor to overheat.

Step 4 - Check Electrical Connections

Make certain that the electrical wiring and connections on your swamp cooler motor are secure and not overheating themselves or shorting out. Also, a bad switch in the swamp cooler motor or fuse can cause the motor to get hot and shut off. Make sure that all connections, switches and wires are correctly installed and maintained to avoid the swamp cooler motor from overheating.

Step 5 - Check Proper Voltage

The motor in your swamp cooler is set to run at or below a specific voltage, preferably below. If too much voltage is put to the motor, it can overheat. Too much voltage can cause damage to internal wiring and circuitry. Make sure that the proper voltage for the motor is what is being applied to avoid damage and overheating. The Voltage capacity for the motor will be printed on the side of the motor. Note that the listed voltage capacity of the motor is not the correct working voltage of the motor. To run properly and not overheat, the motor should run at 55 to 60 percent of the total voltage capacity.