  The solar neutrino flux arrives at Earth as an incoherent admixture of mass
eigenstates, and then solar neutrino detection constitute a blind probe to the
oscillation pattern of the neutrino flavour conversion. Consequently, it is
also impossible to probe, in a model independent approach, any new physics that
leads to an enhancement of decoherence during the neutrino evolution, an effect
that is present for instance in Open Quantum System formalism. However, such
mechanism can also induce changes between mass eigenstates if an energy
interchange between the neutrino subsystem and the reservoir is not explicitly
forbidden. In this work the conversion probabilities between mass eigenstates
in an Open Quantum System are calculated, and limits are stablished for these
kind of transitions. We present our results in a pedagogical way, pointing out
how far the analysis can go without any assumption on the neutrino conversion
physics inside the Sun, before performing the full calculations. We obtain as
limits for the decoherence parameters the values of $ \Gamma_3< 6.5\times
10^{-19}$ eV and $\Gamma_8< 7.1\times 10^{-19}$ eV at 3$\sigma$.
