Although a-SiC:H is a promising material for the fabrication of visible light emitting devices, their performance are easily degraded by charged particle or light irradiation. We report on this effect induced by H and He ions and by light of different wavelengths. The details of the dependence of the formation of defects on the ion-energy deposition will be presented. In particular, we will show that defects can be formed in the inelastic regimes. By measuring the concentration of defects, we will show that the mechanism of tunnelling to defects governs the luminescence quenching and the relevant material parameters can be obtained. Similarly, the mechanism of light-induced defect formation will be elucidated by its power and wavelength dependence. Comparison with the available models clarifies that the light-induced reconfiguration of defects is the mechanism of non-radiative trap formation.