The 4 most common part(s) or condition(s) which cause the symptom Dryer won't start are listed below starting with the most likely. Check or test each item and watch any available videos.
RepairClinic Item # 2997778
The thermal fuse helps to prevent a dryer fire by shutting off power to the dryer if it overheats. If the dryer won't start check this fuse first. Test the thermal fuse with an ohm meter or continuity checker. This is the most common part to fail when the dryer won't start. Once the thermal fuse has blown, it has to be replaced. It can not be reset.
RepairClinic Item # 1227441
The door switch is located near the dryer door and is activated when the door is closed. If the door switch fails, the dryer won't start at all. Most door switches will make an audible click when they are activated. If the door switch makes a clicking sound when activated it is probably not defective. If it doesn't make a click, it can be checked with an ohm meter or continuity checker. The door switch is relatively easy to replace and is usually not very expensive.
RepairClinic Item # 1226688
On most dryers the drive motor turns the drum and the blower wheel to exhaust the air. If the dryer won't start the motor might be defective. Before replacing the motor, check the thermal fuse, start switch and door switch because all three are more likely the cause. If the dryer won't start and the dryer motor makes a humming noise there might be something caught in the blower wheel, or the drum might be binding. Try removing the belt from the motor and checking the blower wheel for obstructions. The dryer motor can't be tested easily. If the more common components have been checked and it seems the motor itself is defective, it will need to be replaced. It is not serviceable.
If the dryer won't start, check to make certain there is electricity to the dryer. For a gas dryer, unplug the dryer from the wall and plug something else into the outlet to see if it's working. For an electric dryer, check the home circuit breaker or fuses. If they are working, check the outlet where the dryer plugs in with a volt meter. There should be between 208 and 240 volts. If there is power to the dryer, check the more common items in this troubleshooting guide.