The part(s) or condition(s) listed below for the symptom Bath fan doesn't vent to the outside are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
Check to see if the fan blade is spinning when the bath fan is turned on. If the fan blade does not spin, make sure that the fan motor is getting power. If the fan motor is not getting power, test the switch for continuity. If the fan motor is getting power, but the fan won’t turn, the fan motor is likely defective.
First, use a rag to clean the vent grille cover and the fan components. If you have cleaned the fan, but the fan still doesn’t vent to the outside, check the vent to determine if it is clogged.
Try spinning the blower wheel by hand. If the blower wheel does not spin freely, check for the blower wheel for obstructions. In addition, ensure that the blower wheel is not rubbing against the blower housing. If the blower wheel is clear of obstructions, but it still doesn’t spin freely, replace the blower wheel.
Make sure that the fan blade is tightly fastened to the motor shaft. If the fan blade is not fastened properly, try to tighten it. If the tightening the fan blade isn’t effective, replace the blade.