We characterized the temperature dependence of electrical resistivities and deep levels in semi-insulating 6H–SiC bulk wafers. Two of the three wafers characterized showed n-type conductivity while the third showed p-type conductivity. We measured the temperature dependence of the resistivity (ρ) and estimated its activation energy for all the samples. On the basis of the deep level parameters obtained from current deep level transient spectroscopy and photoinduced current level transient spectroscopy, we were able to reproduce ρ for n-type samples but not for the p-type sample. These results suggest that although the deep levels observed in this study have significant effects on ρ for semi-insulating n-type 6H–SiC, there are unobserved deep levels compensating acceptors.