01 S60 air conditioning blower

It is designed this way to ensure that a heat surge does not occur in the coolant system. It puts the fan on when the coolant is hotter than normal, like after a fast run to the shops without idling the engine before switching off. When the motor stops there is no cooling airflow through the radiator and the heat will continue to build so the fan comes on to keep this heat rise under control. The vast majority of modern vehicles are designed to do this, particularly compacts and UK & Japanese cars where the radiator size is limited by underhood space.

All the best, Peter.