The fan is driven by the fan control module (shouldn't be a surprise ), item 4/31 in the attached drawing.
This is essentially a power transistor, I think that in V70 models it is located at the bottom of the fan unit (has a cooling surface and two connectors, a 4 way and a 2 way). If this transistor fails (possibly by not replacing the pollen filter on time, resulting is a constant high current need for the fan to get enough air circulation), it can do so by shorting emitter to collector, resulting in a constant high current and thus running fan. As can be seen from the drawing, the fan control module has a constant power connection so a failing transistor will keep the fan running even when the car has shutdown.
Although a failing fan module is not the only possible cause of a continously running fan, I think it is worth looking into. In the mean time you may consider to remove fuse 11C/26, as the drawing shows it feeds the fan motor, I think it has no other circuits to feed. Note that the drawing is that of a manual climate control, the fan is controlled in the same way in case of an automatic airco.
144 GL (1974)--->244 GL (1982)--->940 GLE 2.3i (1992)--->XC70 2.5T (2004)