I had this problem with my Tumble. I replaced the thermostat twice with a new one.I also
replaced the heater element as a precuation, this did not fix the issue. I found that cleaning the condenser filter by running water through it fixed the problem for me. Tumble has been running for a month now with no further problems. Note: You can reset the thermostat by dropping it from approximately 12 inches on to something hard.
Jason Rodber, January 2013