Bathroom vent fans are important parts of any bathroom that has a shower. Without a working vent fan, bathrooms will get very damp from the shower steam, and mould and/or mildew will grow. If your bathroom vent fan works but does so with protests (i.e. squealing or squeaking), it will need to be oiled before it will return to quiet operation.
Switch off the power for the vent fan at your circuit breaker.
Unscrew the vent fan wall plate and remove it from the wall. Then, pull the fan motor out of the wall.
Unplug the power cable from the motor or disconnect the power wires by unscrewing the screws that connect them to the motor.
Remove the vent fan blade from the motor, and wipe the dust off the entire motor and fan blade with a damp rag. Then, hold the blade under running water (bathtub or sink) and wipe it until it's clean.
Dry the vent fan blade and the entire motor assembly. Clean out the spot in the wall where the vent fan goes using a vacuum cleaner and attachment.
Clean the motor shaft with a rag. Drip some lubricating oil (number 30 is recommended) onto the shaft and work it in by turning it around several times by hand.
Replace the vent fan blade, test it with your hand and reconnect the vent fan motor to its power cable or wires. Then put it back in its spot in the wall and replace the wall plate.
Switch the power back on at the circuit breaker. Turn on your bathroom vent fan to test that it has stopped squealing.