Why does the fan keep coming on on my citroen picasso?

The fan in your Citroën Picasso may keep coming on due to several reasons, such as the engine overheating, a malfunctioning temperature sensor, or a faulty thermostat. It could also be triggered by the air conditioning system running, as the fan helps cool the condenser. Additionally, a problem with the fan relay or wiring could cause the fan to operate continuously. It's advisable to have the vehicle checked by a professional to diagnose and resolve the issue.