Check the connection to the AC power outlet.
Make sure circuit breakers or fuses controlling the AC power outlet have not tripped or blown.
Allow the sander to cool down if it has overheated from heavy use and tripped the thermal protection switch.
Allow the sander to warm to room temperature if it has been stored in a cold environment.
Evaluate the extension cords in use. Extension cords with strands less than 2.5 mm in diameter should not be used. Excessively long extension cords should not be used.
Test the tension of the V-belts driving the drum. Adjust it according to the manufacturer's recommendations.
Make sure the drive elements are not binding or sticking.
Verify that the abrasive grit of the sanding belt is not too coarse for the wood surface being sanded. Substitute lighter grit if necessary.
Allow the sander to warm to room temperature if it has been stored in a cold environment.
Evaluate the extension cords in use. Extension cords with strands less than 2.5 mm in diameter should not be used. Excessively long extension cords should not be used.
Test the tension of the V-belts driving the drum. Adjust it according to the manufacturer's recommendations.
Look for excessive wood dust or dirt deposits on the sanding drum and tensioning rollers.
Inspect the sanding belt for damage.
Make sure the sanding belt is tracking correctly. Adjust if necessary.
Look for blockages or deposits in the motor air intake duct or fan housing.
Verify that the dust bag is not over-filled, incorrectly mounted or damaged.
Check the integrity of the bumper sealing felt that seals the drum housing to the floor surface.
Look for blockages anywhere in the suction system and clear them if necessary.
Check the tension of the V-belt that drives the suction system and adjust it if necessary.
Make sure the side cover of the machine is correctly installed.
Inspect the sanding belt and sanding drum for damage.
Verify that the abrasive grit of the sanding belt is not too coarse for the wood surface being sanded. Substitute lighter grit if necessary.
Make sure the wheels are not damaged, dirty or greasy.
Test the tension of the V-belts driving the drum. Adjust it according to the manufacturer's recommendations.
Check the integrity of the linkage from the lowering lever to the drum-lowering mechanism. Make sure it is not binding or inoperative.
Verify that the sanding drum pressure setting is correct.
Make sure that the operator is not pushing too hard on the machine during sanding or using some other improper work method.