The lamp is defective.
To change the lamp, proceed as follows:
Before changing the lamp, unplug the appliance from the socket. Alternatively, disconnect the mains fuse.
Open the appliance door.
Unscrew the cap that is located above the door opening inside the tumble dryer.
Replace the lamp.
Put the cap back in place.
Retighten the cap.
Make sure that the cap is seated securely. If the cap is loose, there is a risk of moisture entering and causing a short circuit.