Cycling Thermostat

• A typical dryer has at least three cycling thermostats -- one for each heat setting option. A thermostat tells the heater to turn on and off based on the temperature it detects in the drum. However, if one of these thermostats breaks, it likely won’t be able to tell the heater to generate heat. Since most timed and automatic drying cycles don’t actually begin until the dryer reaches a desired temperature, a broken thermostat might explain why the dryer won’t heat and its knobs won’t advance. Reset your dryer for a different heat setting and see if the problem persists. If the dryer acts normally on another setting, the cycling thermostat for the original heat setting you chose is bad and needs to be replaced. However, if the problem remains after you've tried to run your dryer on another heat setting, the cycling thermostats are probably fine and the problem is with another component.
  
  

Thermal Fuse

• A dryer will sometimes have a thermal fuse; if it fails, it will shut off the heater and occasionally the dryer. The fuse is connected to a safety thermostat that will activate the fuse if the dryer’s temperature gets too hot. A dryer won’t work properly after the fuse blows; it probably won’t heat and consequently its knobs may not move, at least not on their own. Replacing the fuse is the only way to restore your dryer’s normal use.
  
  

Heater

• A burned-out heating element could be the reason why your dryer won’t heat. The heating element is a coiled wire that conducts heat when energized by electricity or gas, depending on your dryer type. If the element fails, the temperature in the drum won’t elevate to a point that the dryer’s cycle and timer knobs advance, since they’ll progress only when the drum’s temperature has reached the set level required for drying. Contact a dryer repair specialist to inspect the heating element. A partially or fully "faded" heating coil will warrant replacement, as the component generally can’t be repaired.
  
  

Loose Connection

• A loose connection inside the dryer’s control console could explain why the dryer isn’t heating and its knobs won’t move. Once you push the dryer’s start button, the controls direct the dryer to heat and tumble. Yet these actions might not happen fully if there’s a loose or faulty wire connection that’s preventing the signal from reaching all the dryer’s components. As a result of a dryer failing to heat, its knobs also won’t move. Contact a dryer repair specialist to review the connectivity of the control panel and repair a connection if the specialist finds a flaw.