Most homes have at least one exhaust fan in the attic. Depending on the size and shape of the attic, the attic may have 2 or 3 fans. Since the attic is usually hot in the summer months - sometimes reaching as much as 130 degrees F - the attic fans will often have bearing failure. The bearings are usually of the sealed type and can not be lubricated. Most of the time it is cheaper to replace the fan than try to repair them. Some fans have a thermostat that can fail but you may not find the correct thermostat and it is still easier to just replace the complete fan.
The tools required to replace the exhaust fan are: flashlight, wire strippers, needle nose pliers, screw drivers and nut drivers.
To replace the attic fan, first verify that the power is turned off. You can turn the breaker off or if the breaker is not marked, using a multimeter, verify the voltage is off by shutting the breakers off one at a time and reading the voltage at the fan connections. ( They are usually connected with wire nuts that you can carefully remove to check the voltage. After the power is turned off and verified disconnect the wires from the fan. The wires may be physically attached to the exhaust fan by a clamp which can be loosened to pull the wire out of the fan. Most fan motors have 3 screws holding them to the housing. Remove the mounting screws and pull thefan out. By doing this you do not have to climb a ladder on outside to remove the exhaust fan. Then reinstall the fan with the mounting screws and reconnect the wires. Turn on voltage and verify that the exhaust fan is working and you are done.
I am a retired electrician with over 3o years experience.
For more information visit http://householdelectricalrepairs.com/