The Electrics

• If your fan does not move when turned on and exhibits no sign of power whatsoever, check the electrics. Check both the plug and the cord for any damage such as separation, torn insulation or broken wires. Many times the plug can go bad from repeatedly pulling on the cord. Replace it since they are not the easiest things to check for continuity.
  
  The switch on a desk fan is another electrical problem to check with a simple AC voltage tester. Place one testing lead on each side of the switch, turn the switch on and if there is no voltage reading, the switch has probably gone bad.
  
  

The Motor

• There are two components to the motor: the actual electrical windings and the motor bearings. If you have determined that power is getting to the motor but the motor doesn't turn, the windings have probably burned out, and the motor needs to be replaced. Since desk fans are so inexpensive, at this point it would most likely be cheaper to just buy another fan.
  
  If there is power in the motor and the fan blades turn very slowly, the bearings might need to be lubricated. This is easier than it sounds. Virtually any spray lubricant will work, just spray a little lubrication on the axle attached to the fan, and allow it to drip down towards the motor. This action will coat the bearings and make them slippery again. Perform the same procedure on the rear axle. Spin the fan with your hand to work the lubrication in, and then turn it on and it will work as good as new.
  
  

The Fan Blades

• If your fan spins freely but there is not very much air coming off the blades, they are probably dirty and should be cleaned. The more gunk that builds up on the blades, the less efficient they become and the less wind they will produce. Cleaning the blades is simple. Unplug the fan, remove the blade guard, dip a rag in some warm soapy dishwater and wipe the blades down. After this, they will blow as good as new.