Posen, S. Hall, D.L. Liepe, M. Melnychuk, O.S. Romanenko, A. Sergatskov, D.A. Trenikhina, Y. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-TUPB049 English 681-685 TUPB049 cavity niobium electron SRF accelerating-gradient Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-TUPB049 http://srf2015.vrws.de/papers/tupb049.pdf The first 1.3 GHz single cell Nb₃Sn cavity coated at Cornell was shown in RF measurements at Cornell and FNAL to have poor RF performance. Though subsequent cavities showed much higher quality factors, this cavity exhibited Q₀ on the order of 10⁹ caused by strong heating concentrated in one of the half cells. This paper presents an investigation into the source of this excess heating, for the purpose of process improvement, so that similar degradation can be avoided in future coatings. Through the use of temperature mapping both at Cornell and at FNAL, locations with high and low surface resistance were located, cut out from the cavity, and studied with microscopic tools. We present the RF measurements and temperature maps as well as the microscopic analyses, then conclude with plans for continued studies.