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Bathroom and sanitary

How can I fix my bathroom exhaust fan? It won't stop running.

Anonymous user 09/07/2026 - 9:17 AM

My bathroom fan usually turns on automatically with the light switch but now it won't turn off after a while like it used to. There's a separate switch for the fan but that doesn't work to turn it off either. To stop it, I've had to cut the main power, and it took about 2 hours to kick in. This issue just started yesterday. Could there be an electrical problem? I haven't noticed any other electrical issues in the house. Or could something like a blockage be the cause? The fan seems pretty clogged with dust and fluff. I'd like to get some advice before I try opening it up or cleaning it. What can I try doing on my own? Thanks.

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5 Answers

Marshal Electric

Rating: 5 out of 5
Edmonton
The issue you are having is an auxiliary fan switch is installed somewhere else in your home that is providing power to your fan dependently of your bathroom switch. This auxiliary circuit is know as a furnace / bath fan interlock. The purpose of the interlock is to provide whole house ventilation with the bath fan acting a primary exhaust for the house and the furnace fan running in order to draw in fresh air to the living space. These systems are commonly misunderstood by home owners and trades people and are there for both inappropriately used installed. I hope that helps sort it out.
Answered8 July 2026
1

GTA Handy Pros

Rating: 5 out of 5
Toronto
To fix this: Turn off the breaker and pull the plastic cover grille straight down. Vacuum out all dust and fluff from the blades and the interior housing to clear the sensor. Locate the tiny humidity dial inside the metal housing and turn it down to its lowest setting. If cleaning fails, the internal sensor board is broken, but you can simply unplug the fan motor from its hidden internal outlet inside the ceiling box to kill the power permanently without affecting your lights.
Answered30 June 2026
0

Alireza Shamshiri

No reviews yet

Thunder Bay
Since the fan used to turn off normally and has just started running continuously, the most likely causes are a faulty timer/humidity sensor, a stuck relay inside the fan, or a defective wall switch. A heavy buildup of dust can also affect some humidity-sensing fans, so cleaning the fan (with the power turned off at the breaker) is a good first step. If the fan still won't shut off after cleaning, it should be inspected and tested by an electrician. Avoid leaving the circuit powered off for long periods, as the bathroom ventilation may be required to control moisture and prevent mold.
Answered7 July 2026
0

Marc Lamoureux

Rating: 5 out of 5
Ottawa
I would check the fan switch and make sure that it works properly
Answered8 July 2026
0

Gorilla Repairs

Rating: 5 out of 5
Etobicoke
Seems the humidity sensor module inside the fan housing has failed. Sometimes it happens simply because it is clogged with years of thick dust! Just turn off the breaker, pull down the plastic fan cover, give it a good vacuuming, and potentially ordering a new sensor module from the fans manufacturer to plug in
Answered9 July 2026
0