Dago did a wonderful job, he explained exactly what he was going to do and wanted me to stay with him so he could show me, I learned somethings. He was very through and professional in doing his job. I felt very good with the results and also the prompt service provided by Sierra Air. I call at 4:15PM thinking someone would come the following day, but Dago was there within the hour, took care of the problem and we had heat again