Low temperature photoluminescence (LTPL) measurements have been performed on 6H, 4H, and 15R polytype SiC crystals. In addition to well-known emission lines close to the band gap a couple of new features could be observed. Emission lines attributed to the recombination of bound excitons at aluminum acceptors have been seen in all three polytypes. A defect interpreted as a divacancy is described for SiC(4H). In SiC(6H) emission lines due to scandium centers have been observed. Furthermore the effect of a uniaxial stress on the LTPL spectrum is investigated.