Not Heating Enough
A malfunctioning limit thermostat may be the culprit if your dryer doesn't get hot enough. Sometimes the thermostat gets stuck in the open position, telling the dryer that the inside of the dryer is already warm enough. Until the limit thermostat is replaced, the dryer will not heat properly.
Overheating is essentially the opposite problem of a dryer that doesn't heat enough. In many cases, the thermostat is stuck in a closed position, telling the dryer that it is not yet hot enough inside. Again, this is usually a problem of the limit thermostat.
A dryer that does not start can be suffering from a variety of problems. Before a dryer will start, it generally has several different safety items that must be in the correct position. A dryer cannot start if the door switch is open, fuses are not functional or thermostats are bad.
Dryers with automatic cycles may run nonstop if one or both of the thermostats have gone bad. During an automatic cycle, the dryer checks its internal temperature and advances the timer if it is high enough. When a thermostat is malfunctioning, it cannot read the internal temperature of the dryer correctly, keeping the timer from moving forward.