  An investigation of the dynamo instability close to the threshold produced by
an ABC forced flow is presented. We focus on the on-off intermittency behavior
of the dynamo and the counter-effect of the Lorentz force in the non-linear
stage of the dynamo. The Lorentz force drastically alters the statistics of the
turbulent fluctuations of the flow and reduces their amplitude. As a result
much longer burst (on-phases) are observed than what is expected based on the
amplitude of the fluctuations in the kinematic regime of the dynamo. For large
Reynolds numbers, the duration time of the ``On'' phase follows a power law
distribution, while for smaller Reynolds numbers the Lorentz force completely
kills the noise and the system transits from a chaotic state into a ``laminar''
time periodic flow. The behavior of the On-Off intermittency as the Reynolds
number is increased is also examined. The connections with dynamo experiments
and theoretical modeling are discussed.
