When designing houses, the mandatory availability of ventilation in utility rooms, kitchens and, of course, bathrooms and toilets is taken into account. This is necessary to ensure natural air exchange in these rooms.

For the bathroom and toilet, it is due to ventilation that normal air humidity is maintained, timely evacuation of exhaust air and its replacement with clean air.

If the fan in the bathroom does not work well, then air stagnation is inevitable, which in the near future will result in the appearance of mold and mildew and negatively affect the decoration of this room.

An extremely unpleasant situation, is not it?

However, what to do in this case and how can it be prevented?

6 Ways to Diagnose a Broken Bath Fan

  1. Check the power supply: Ensure that the fan is still receiving power. Ensure that the circuit breaker or fuse for the bathroom fan is not tripped or blown. If it is, reset the breaker or replace the fuse.
    Check the power supply
  2. Check the switch: Verify that the fan switch is in the “on” position. Sometimes, a switch can become loose or faulty, preventing the fan from turning on.
    Check the switch
  3. Inspect the fan grille and blades: The fan might be jammed due to dirt, debris, or other obstructions in the grille or blades. The power was turned off to the fan, and the grille was carefully removed to check for any debris. Clean it thoroughly and make sure nothing is hindering the fan’s movement.
    Inspect the fan grille and blades
  4. Test the motor: If the power supply and switch are fine but the fan still does not work, the motor may be the issue. Try turning the fan blades manually; if they spin freely, the motor may be faulty and need replacement.
    Test the motor
  5. Check the wiring: Wiring issues could also be a potential cause. If you are comfortable working with electrical components, you can inspect the fan’s wiring for any loose connections, damaged wires, or faulty switches. If you’re uncertain about handling electrical work, it is best to consult a professional electrician.
    Check the wiring
  6. Verify the exhaust duct: Check the exhaust duct connected to the fan. Sometimes, blockages or restrictions in the duct can put strain on the fan motor, causing it to stop working. Clear any obstructions in the duct to improve airflow.
    Verify the exhaust duct


If you have tried the troubleshooting steps above and the fan still does not work, it may be time to consider seeking the assistance of a qualified electrician or HVAC technician. They can diagnose the issue more accurately and recommend appropriate repairs or replacements.

Please remember that when dealing with electrical components, safety should always be the top priority. If you are unsure or uncomfortable with any part of the troubleshooting process, it is best to seek professional help.

How in general can you determine if the fan is truly functioning?

Special diagnostics aimed at checking the traction will help to assess the condition of the ventilation system. The event is held in several stages with the help of improvised means or special devices.

It is better to check the operation of natural ventilation in the cold season. Before that, it is recommended to ensure the flow of fresh air: open the window pane or install windows in the ventilation mode. In sanitary rooms, the door should be slightly opened.

Check vent
The easiest way to diagnose at home is to check with fire. You need to take a lighted match, lighter or candle and carefully bring the flame to the grate of the ventilation duct that drains the exhaust air from the bathroom.

The functionality of the vent channels is evaluated by the behavior of the flame brought to the grate:

  • deviates to the side of the grid – the system is working, and the thrust is normal;
  • remains in the same position – there is no traction;
  • deviates towards the room – there is a reverse thrust.

It is worth considering that this technique is unsafe and is highly not recommended for use by gas service specialists. If there is a leak in the house, gas accumulates in the ventilation shafts. In such circumstances, an open flame can trigger a fire or explosion.

  A safer way is to test with a thin sheet of paper. As in the previous case, it is brought to the vent. The paper is taken by the lower tip and held in an upright position near the grid.  

If the paper is strongly attracted to the grate and is held on it, ventilation works well. A short-term sticking or a slight deviation towards the hole indicates a weak pull. If nothing happens and the sheet remains stationary, the system is faulty. Paper repulsion is a sign of reverse traction

The outflow of air can also be felt thanks to tactile sensations. To do this, wet your hand and bring a wet palm to the vent. The presence of air flow is determined by the cooling blow.

These diagnostic options will give only a general idea of the efficiency of ventilation in the bathroom. It is possible to obtain a quantitative assessment of the effectiveness and determine the compliance of the state of the system with the norms using special devices – anemometers.

  Anemometers measure the air flow rate in the ventilation duct. They are often used by professionals, but simple models are quite suitable for use at home.   

The device is brought to the ventilation grate at the distance specified in the instructions. After a few seconds, the air flow velocity indicator (V) is displayed on the display. Having fixed the received figure, it is necessary to calculate the volume of air passed through the system according to the formula:

Q = V x S x 360,


  • S is the cross–sectional area of the ventilation duct in m2;
  • V is the air flow velocity.

The result is compared with the normative parameters. The optimal value for a bathroom is 25 m3/h. The norm for combined bathrooms should be twice as large.

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