When the fan runs—but the bathroom still doesn’t work.

Start with the symptom, then check the simplest and safest causes before blaming the fan.

Humidity remains

Fan runs, room stays damp

Likely causes include insufficient runtime, low delivered airflow, no makeup air, or an oversized moisture load.

Check first

Run the fan during bathing and for 20–30 minutes afterward. Crack the door and see whether performance improves.

Then inspect

Check duct restrictions, the exterior damper, airflow setting, room size, and shower enclosure.

Noise

Fan is louder than expected

Vibration, turbulence, a loose grille, or duct pressure can turn a quiet motor into a noisy installation.

Check first

Confirm the grille and motor assembly are seated, and listen for contact with framing or duct.

Then inspect

Look for tight elbows, reduced duct, crushed flex, and a restrictive hood.

Airflow

Weak suction at the grille

The fan may be starved on either side: no replacement air entering the room or too much resistance leaving it.

Check first

Open the bathroom door slightly. Verify the exterior damper opens fully.

Then inspect

Check the CFM selector, duct connection, accumulated debris, and the entire exhaust path.

Exterior

Damper will not open

Paint, caulk, corrosion, nesting material, ice, or poor installation can hold a flap closed.

Check first

With the fan on, observe the termination from a safe location. Do not work at height without proper equipment.

Then inspect

Clean or repair the hood and verify it provides adequate free area.

Condensation

Water drips from the fan

Warm moist air can condense inside a cold duct, especially in unconditioned spaces.

Check first

Stop using the fan if water is near electrical components and disconnect power safely.

Then inspect

Look for missing duct insulation, low spots, exterior backdraft, or a route that traps condensate.

Fog

Mirror stays foggy

A foggy mirror alone does not prove fan failure, but persistent moisture on walls and ceilings warrants investigation.

Check first

Use the fan earlier and longer; open the bathroom door after bathing.

Then inspect

Assess delivered airflow, fan location, room temperature, and moisture generation.

Safety boundary

Know when to stop.

Turn off power and call a qualified professional for burning odors, arcing, hot wiring, repeated breaker trips, water near electrical parts, inaccessible roof work, or uncertain wiring.

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Five-minute airflow diagnosis · video placeholder