It sounds as though the temperature switch is either stuck or broken. Unplug the machine and remover the panel at the back . Above the heating element you will see the temperature switches . Most models have two. The surface of the switch should be able to be pushed in gently and an audible "click" can be heard. If it is stuck in , a paper clip can be gently pushed through the hole in the rear of the switch to free it off. If this fails either the element is burnt out or one of the switches requires replacing.
compostheap, September 2008