The Francis turbine runners of the four ternary groups of Grimsel 2 power plant in Switzerland showed fatigue cracks at the runner blades much earlier than expected. To find the source of these cracks, strain gauges and accelerometers were used to get information about the harmful stresses on the runner during operation. It is observed that the speed no-load operation during the start-up and the shutdown processes of the turbine impose large stresses on the runner blades.