Simple checks

• When troubleshooting an appliance, start with the simple things first. If the machine is not fully drying the clothes, make sure there aren't too many items packed in the dryer. Too many articles of clothing in the dryer will affect drying time. You may think you are saving time by packing as many shirts in the dryer as you can, but you are just making it more difficult to dry and wasting energy.
  A clogged dryer filter also reduces your dryer's efficiency. Check the lint trap and clean it out. Check and clean this filter before every load. Besides causing damp clothes, a clogged lint filter can be a fire hazard.
  One last simple check is the exhaust duct. This duct, located at the back of the dryer, exhausts hot air from the house. The dryer will have a hard time getting to the optimal temperature if this duct is clogged or kinked.
  
  

Broken belt

• If the clothes inside the dryer are not turning, you probably have a broken belt. The items in the dryer won't fully dry if they aren't spinning. The inside of the dryer, called the drum, turns with the help of a belt.
  Unplug the dryer and turn off the power before working on any appliance. To find out if the dryer drum has a loose or broken belt, open the top of the dryer. Take out the lint trap and remove the two screws located at the lint trap. Find two clips at the front of the dryer that keep the top on. Slip a screwdriver in to this portion of the dryer and pop the clips open. You will now be able to open the top of the dryer and see if the belt is loose, broken or fallen off. Purchase a new belt at a hardware store. Select a belt designated for your particular make and model.
  
  

Controls

• If it is not a filter or belt problem, consider the dryer controls. Dryers contain several different types of controls that can malfunction, causing a dryer to lose heat. Review the manufacturer's guide to find out where the controls are located.
  Some controls that affect drying include the temperature selector switch, the thermostat or the centrifugal switch. Once you locate these controls, use a manometer to check for voltage. Most of the controls should show an infinity reading on the manometer. If they don't, the control probably needs to be replaced.
  If you have a digital dryer, you may be in luck. On some newer digital dryers, the consumer can enter diagnostic codes located in the manufacturer's directions to find out if a particular control has failed. If that code comes up on the dryer, there is no need to troubleshoot any further. Just replace or repair the control.