  Studies of magnetic induction in von K\'arm\'an swirling flows have so far
linked the time-averaged induced magnetic field to the structure of the mean
flow. They have evidenced the Omega and Parker mechanism generated respectively
by the flow differential rotation and helicity, which underly the Duddley and
James \cite{DuddleyJames} dynamos. Using an array of Hall probes we study here
the dynamical regime. In the experimental flow, turbulence is fully developed
and large fluctuations are observed in the magnetic induction processes. We
find that the large scale turbulent fluctuations have different characteristics
when induction results from the differential rotation or from the dynamics of
the stagnation point in the mid plane of the von K\'arm\'an flow. Symmetry
considerations indicate that the dynamical flow spends half of its time away
from the time-averaged structure. The consequences of these observations for
dynamo experiments are discussed.
