How to Fix a Bathroom Exhaust Fan That Works Intermittently

A bathroom exhaust fan that works intermittently can be frustrating. One day it runs fine, the next it barely turns on, or shuts off in the middle of use. Whether it’s powering up sporadically, turning off on its own, or failing to start unless you flip the switch multiple times, an unreliable fan isn’t just inconvenient; it can also affect air quality, moisture control, and even indicate deeper electrical or mechanical problems.

The good news is that an intermittent fan often has a fixable cause. You don’t need to replace the entire unit right away, and with some basic troubleshooting steps, you can usually pinpoint the problem or at least determine whether a repair or replacement is in order.

This guide will walk you through the most common reasons a bathroom fan works on and off, how to diagnose them safely, and what steps to take to get your fan back to dependable performance.

The information in this article may not apply to your specific appliance model. We recommend consulting your manufacturer’s documentation or contact us with any questions.

Why Fixing Your Fan Matters

An exhaust fan does more than move air. It prevents condensation, reduces mold and mildew buildup, and helps eliminate odors and pollutants. When your fan doesn’t work consistently, moisture can build up on surfaces like drywall, mirrors, and windows, leading to long-term damage or indoor air quality issues.

More importantly, an intermittent fan could be a sign of:

• A failing motor or internal component
• Loose wiring or a bad connection
• A faulty switch or timer
• Electrical issues within the circuit
• Overheating or blocked airflow

These problems, if ignored, could eventually cause the fan to stop working completely, or worse, present a fire hazard.

Step 1: Observe When and How the Fan Fails

Before grabbing your tools, take a moment to observe exactly how the fan is misbehaving. This can help you narrow down the possible cause.

• Does the fan turn on, then shut off on its own?
• Does it sometimes not turn on at all?
• Does it only work after flipping the switch multiple times?
• Does it make unusual noises before stopping?
• Does it stop after running for a certain amount of time?

Make note of patterns. For example, a fan that stops after five minutes every time could be overheating. One that fails to turn on unless you jiggle the switch may have a bad connection.

Step 2: Check the Switch and Power Source

Sometimes the issue isn’t with the fan itself but with the switch or the power supply. This is especially true if you’re using a timer switch, smart switch, or motion sensor.

Turn off the breaker to the bathroom and remove the switch cover. With a non-contact voltage tester, verify that no current is running through the wires.

• Inspect for loose, burnt, or corroded wires.
• Make sure wire nuts and terminal screws are tightly secured.
• Check for signs of overheating or discoloration on the switch.

If you have a timer or smart switch, consider replacing it with a simple on/off toggle temporarily. If the fan starts working reliably with a basic switch, the issue may lie in the control device itself.

Also, if the fan and light are on the same switch and only the fan is malfunctioning, that suggests the issue lies in the fan wiring, not the power supply.

Step 3: Test for Overheating

Fans with older motors or clogged housings can overheat. Many units include a thermal cutoff switch, which shuts down the motor to prevent damage when temperatures get too high.

When this happens, the fan may:

• Start normally, then shut off after several minutes
• Refuse to restart until it cools down
• Work better on cooler days or in short bursts

To check for overheating:

1. Turn off the power and remove the fan cover.
2. Clean the blades, housing, and motor with a vacuum and soft brush.
3. Ensure the fan spins freely by hand. If it feels stiff or wobbly, the bearings may be failing.
4. Plug the fan back in or reconnect the wiring and run it again while observing performance.

If the fan works but shuts off after a few minutes, it’s likely overheating due to age, dust buildup, or motor wear.

Step 4: Look for Loose or Damaged Wiring

An intermittent electrical connection is a common cause of fans that power on and off without warning.

Inside the fan housing, check:

• The wire connections between the fan and the supply line.
• The condition of wire nuts and any signs of arcing or corrosion.
• Any exposed or frayed wire insulation.

If you find loose wires or scorched insulation, you’ll need to disconnect the power and repair or replace the damaged section. Be sure to use appropriate connectors, and never leave exposed copper wire inside the housing.

Also, check the connector that powers the fan motor itself. In some models, this is a plug-type connection that can work loose over time due to vibration.

Step 5: Inspect the Motor

If the wiring and switch check out, and the fan is clean and receiving consistent power, the next suspect is the motor itself.

Warning signs of a failing motor include:

• Loud humming or buzzing when it runs
• Slow spin-up time
• Stops running after a few minutes
• Smells of burnt insulation or metal

Some fan motors simply wear out after years of use, especially in humid environments like bathrooms. If the motor shows signs of failure and the unit is older than 10 years, replacing the fan may be more cost-effective than trying to repair it.

However, for high-quality or newer fans, it may be worth ordering a replacement motor if it’s available from the manufacturer.

Step 6: Eliminate External Interference

In some cases, the problem may not be the fan at all, but something interfering with its circuit or operation. These less obvious issues include:

• Voltage fluctuations on the circuit due to large appliances elsewhere in the home
• A shared circuit with too many high-draw devices (like space heaters or hair dryers)
• A faulty breaker that trips or fails to provide a steady current

Try plugging a small lamp or appliance into the same outlet as the fan (if it’s on a shared circuit) and observe whether it behaves erratically. If multiple devices have power issues on the same line, your problem may be in the panel or wiring, not just the fan.

If the breaker itself feels warm or is constantly being reset, that’s a sign it may need to be replaced.

Final Thoughts

An intermittent bathroom fan is more than just an inconvenience; it can be a warning sign of electrical issues or a motor nearing the end of its life. Fortunately, most of these problems can be diagnosed with a bit of time, observation, and basic safety precautions.

Start by examining the simple stuff: the switch, the wiring, and the cleanliness of the fan. From there, rule out overheating or electrical inconsistencies, and keep an eye out for wear and tear on the motor or moving parts. If you’re not confident in what you’re seeing, or if the fan continues to behave erratically, don’t hesitate to bring in a professional for a full inspection.

Ultimately, your bathroom fan should be something you turn on and forget about, not something you second-guess every time you flip the switch. With the right approach, you can get back to reliable ventilation and better indoor air quality in no time.

Where To Find Us 

If you need any replacement parts for your appliances, you can enter your model number at AppliancePartsPros.com to locate and order them quickly. Most orders arrive in just two business days, and we have tons of great information in our repair help section and YouTube videos to help you troubleshoot.

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