A bathroom exhaust fan not working usually falls into one of three cases: it is completely dead, it runs but barely pulls air, or it pulls air that never actually reaches the outside. Only the second and third are things you can mostly check yourself. A dead fan is a power or motor question, and anything past the grille and the breaker belongs to a licensed electrician. Start by holding a single square of tissue near the grille while the fan runs. If the tissue is not pulled against it, the fan is not doing its job, even if it sounds busy.
That noise is the trap. A fan can hum, rattle and spin for years while moving very little moist air out of the room. This guide is about telling those cases apart, doing the safe checks, and knowing where the job stops being yours.
Why it matters that the fan actually moves air
The bathroom fan is a moisture tool first. The U.S. Environmental Protection Agency's A Brief Guide to Mold, Moisture and Your Home (read 2026-09-27) lists "Run the bathroom fan or open the window when showering" among its moisture-control steps, and it recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent relative humidity.
A fan that makes noise but moves little air gives you the feeling of ventilation without the result. Mirrors stay fogged, towels stay damp, and paint on the ceiling starts to peel or spot. Those are the symptoms that usually send people looking for this page, and they are worth taking seriously, because steady moisture is what lets mold settle in.
Bathroom exhaust fan not working: the three cases
Sorting the problem first saves you from fixing the wrong thing.
| What you notice | Likely case | Who handles it |
|---|---|---|
| Nothing happens at the switch, no sound at all | No power reaching the fan, a failed switch or timer, or a dead motor | You check the breaker; a licensed electrician handles wiring, switch and motor replacement |
| It hums or spins but the tissue barely moves | Dust-clogged grille or blades, a stuck damper, a crushed or long duct | Mostly you, for the grille; a contractor or electrician for the duct and fan housing |
| It pulls the tissue, but the room still stays wet | Fan runs too briefly, is undersized, or the duct ends in the attic instead of outside | You, for run time; a contractor for ducting and termination |
The rest of this page follows that table.
Case 1: the fan is completely dead
If flipping the switch produces no sound at all, the problem is almost always electrical: the breaker, the switch or timer, the wiring, or the motor.
What you can safely do:
- Check the breaker panel. Look for a tripped breaker or a tripped GFCI outlet nearby, since some bathroom circuits run through one. Reset a tripped breaker once. If it trips again, stop and call an electrician. If you are not sure how your panel is laid out, our guide on how to read a breaker panel safely explains what you can look at with the cover on.
- Check whether the fan shares a switch with the light. If the light works and the fan does not on the same switch, the switch is probably not the issue.
- Note any timer, humidity sensor or smart control. These add another part that can fail.
Stop here if: the breaker trips repeatedly, you smell burning or see scorch marks around the grille or switch, the fan housing is hot, or getting further means opening the switch box or the fan's wiring compartment. Replacing a switch, a motor or a whole fan involves household wiring, and that is licensed electrician work. Whether that work needs a permit depends on your city or county, so ask your local building department rather than assuming either way.
Case 2: it runs but barely pulls air
This is the most common case, and the tissue test is the quickest way to spot it. A fan that holds the tissue flat against the grille is pulling air. One that lets it drift or fall is not pulling enough.
Clean the grille and what you can reach
Dust and lint build up on the grille and the blades, and they choke airflow. Turn the fan off at the breaker, not just the wall switch, before you touch anything. Most grilles come down by squeezing two spring clips. Wash the grille with warm soapy water and let it dry fully.
If you can see the blades, you can wipe dust off them with a dry cloth or a vacuum brush while the power is off. Do not unplug, unscrew or remove the motor unless your fan's manual shows it as a user step. Many fans have the motor wired in, and that part is electrician territory. If you do not know which fan you have, the label is usually inside the housing once the grille is down; our guide on finding an appliance model number covers where manufacturers tend to put it.
Check the outside damper
Most fans have a backdraft damper, a small flap that opens when the fan pushes air and closes to keep outside air out. Dampers stick, get painted shut or get blocked by nests and debris. If you can see the outdoor vent cap from the ground, check whether its flap moves when the fan runs.
Do not climb onto the roof to check a roof cap. Roof work is a job for a roofer or a contractor. The Department of Energy's Building America Solution Center guide on bathroom exhaust fans (read 2026-09-27) includes checking that "any dampers on the outside termination are able to open freely; and that packing tape is removed" as part of confirming a fan installation. A new fan with packing tape still across the damper will run, sound normal and move almost nothing.
Suspect the duct
If the grille is clean and the damper opens but airflow is still weak, the duct is the likely culprit: crushed, kinked, too long, disconnected or full of lint. The same Building America guide recommends smooth ducting of the diameter the fan maker specifies, run to the outside with "as few bends as possible." Ducting lives in the attic or between floors, which means ladders, tight spaces and often insulation. That is a job to hand to a contractor rather than to troubleshoot yourself.
Case 3: it pulls air but the room stays wet
A fan can pass the tissue test and still lose the fight with a hot shower. Three reasons come up most.
It is not running long enough
The Building America guide states: "It is recommended to leave the fan running for one hour after a shower for effective humidity control." It also recommends controlling the fan with a timer switch rather than a standard wall switch. Most of us switch the fan off as we walk out, which is when the room is at its wettest. Changing the habit is free. Changing the switch is electrician work.
It may be too small for the room
The same guide says bathroom fans "should have a mechanical exhaust capacity of ≥ 50 cfm for intermittent operation or ≥ 20 cfm of ventilation when operated continuously." Those are minimums from that guide, not a sizing formula for your bathroom. The fan's rated airflow in cubic feet per minute (cfm) is usually printed on the label inside the housing. If a larger bathroom has a small fan, that may explain a lot. Choosing and installing a replacement is work for an electrician or a contractor, who can match the fan to the room and the duct.
It may not vent outside at all
This is the one people rarely find on their own. The Building America guide says to "install the fan to vent outdoors, not into an attic, crawlspace, or space between floors." Some older installations blow straight into the attic, or the duct has fallen off the fan and now dumps moist air into the ceiling space. The fan works perfectly and the moisture simply moves upstairs.
You usually cannot confirm this from the bathroom. Signs worth noting: no vent cap anywhere on the outside wall or roof near the bathroom, or frost, damp insulation or staining in the attic above it. Going into the attic means walking on joists, around wiring, and sometimes near older insulation. If your house is older, that insulation is a reason to leave it undisturbed and have a professional look. Rerouting a duct to the outside is contractor work, and termination through a roof or wall may need a permit depending on where you live.
What the checks do not tell you
These checks narrow the problem down; they do not diagnose your house. A weak fan can have two causes at once, such as a dusty grille and a long, sagging duct. And a damp bathroom is not always the fan's fault. Indoor humidity across the whole house, a slow leak, or a cold exterior wall can all keep a bathroom wet no matter what the fan does. Our home maintenance checklist is a good place to add a twice-yearly grille clean and tissue test, so a slow decline gets caught early.
Where this job stops being yours
To put the stop lines in one place:
- You: the breaker check, the tissue test, cleaning the grille with the power off, looking at a vent cap you can see from the ground, and running the fan longer.
- A licensed electrician: anything involving the switch, timer, humidity control, motor, wiring or replacing the fan.
- A contractor or roofer: ducting in the attic, roof or wall terminations, and anything that means walking the roof.
- Your local building department: whether any of that work needs a permit where you live. Rules differ by city, county and state.
FAQ
How do I know if my bathroom exhaust fan is working?
Hold a square of tissue near the grille while the fan runs. If it is pulled flat against the grille, the fan is moving air. If it drifts or falls, airflow is weak, even if the fan sounds normal.
Why is my bathroom fan running but not pulling air?
Common causes are a dust-clogged grille or blades, a stuck or taped outdoor damper, and a crushed, long or disconnected duct. Clean the grille with the power off first; duct problems usually need a contractor.
How long should a bathroom fan run after a shower?
The Department of Energy's Building America Solution Center recommends leaving it running for one hour after a shower for effective humidity control, ideally on a timer switch.
Can a bathroom fan vent into the attic?
The Building America Solution Center says to vent the fan outdoors, not into an attic, crawlspace or the space between floors. Rerouting a duct is contractor work.
Can I replace a bathroom exhaust fan myself?
Replacing a fan involves household wiring, so we route it to a licensed electrician. Whether it needs a permit depends on your local building department.
