How to control your bathroom fan with the light switch

The simplest solution to control a bathroom fan is to connect it to the light switch. It is mostly implemented in windowless bathrooms or for ventilation control in guest toilets. With the light switch, the fan is activated at the same time.

How does a bathroom fan work via the light switch?

Windowless bathrooms or toilets always need a light source. The light in these rooms is activated either via a switch or a motion detector (€ 8.43 at Amazon *), which also has the function of a switch. If a switching process is triggered, the fan starts operating at the same time.

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In the course of a bathroom renovation, it is easy to install a bathroom fan. Only a two-pole cable is required for control via the light switch, with a live conductor and the neutral conductor. The fan contact is coupled to the live conductor, which closes as soon as the light is switched on.

If the bathroom fan has no other functions, it only runs in combination with the lighting. If this is switched off, the fan also stops moving. This is not always cheap, because if you enter the room for a short time, no proper air exchange can take place. Therefore, there are various ways to keep the fan running despite the switch being turned off.

What additional functions are there?

Many fans are already offered with the following additional functions that can be set individually. However, at least a 3-pin connection cable is required to use additional functions.


After-running means that the fan continues to run for a certain time when you leave the bathroom or toilet in order to remove odors and moisture from the room.

Follow-up function with humidity sensor

The humidity sensor works automatically in conjunction with the run-on function. It switches on when the humidity in the room exceeds a certain setpoint.

Switch-on delay

A switch-on delay is appropriate if you want to take a quiet shower without the fan immediately sucking off the warm and humid air.