We first had an appliance repair business come to work on the dryer. The technician replaced the thermal fuse and the dryer appeared to work again. The first cycle after this repair ran very hot and the thermal fuse tripped again causing the C9 error code to reappear.. Guessing the problem was the thermostat not functioning correctly but also that the thermal fuse was tripping before the thermistor cut out, I decided to replace all three items this time. The total parts cost was less than the technician coming to our house again and took about 20 minutes to disassemble the dryer, replace all three parts, and re-assemble the dryer again. Dryer has now worked correctly (back to a normal heat during its running cycle) for 6 loads since the repair. Problem solved.