We propose to obtain the temperature dependence of the diamagnetic spin-precession amplitudes up to 1100 K for the three electrical types of 4H-SiC in order to extract the Mu donor and acceptor ionization energies. With a minor adjustment for site metastability of neutral Mu centers, these energies place the donor and acceptor thermodynamic defect levels relative to the associated band edges. Our main goal is to provide an experimental check of a still controversial theoretical prediction that the defect levels of hydrogen should be centrally pinned at a specific energy independent of host material. Results to date on Mu in Si, Ge, GaAs and 6H-SiC appear to support universality but place the pinned Mu(+/-) level about 0.5 eV above the predicted energy. Comparison of ionization energies in 4H and 6H SiC will test additional assumptions in the theoretical treatment of H/Mu impurities.