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.
The start switch is on the dryer control panel. Depending on the model, either press a button or turn a dial to start the dryer. If the start switch fails the dryer won't start or make any noise. Test the switch with an ohm meter or continuity checker. If the dryer hums when the start switch is activated, or if the motor runs only while activating the start switch, the motor might be defective or something might be binding the drum preventing it from turning freely. If the dryer start switch does not have continuity when it is activated, it will need to be replaced.
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.
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.
On most dryers, if the drive belt breaks the motor can still be heard and it will still be blowing air out the exhaust tube, but the drum will not spin. However, in some dryers when the drive belt breaks the tension pulley arm trips a switch which shuts off power to the entire dryer. If the dryer won't start, check to see if the belt is broken. If it is, replace the belt and the dryer should be fine. If the belt is not broken, check the other components that can fail when the dryer won't start.
Thermal Cut Out Fuse Kit
Most dryers have several temperature control devices such as a thermal fuse, thermal cut out, high limit fuse or high limit thermostat. Some manufacturers sell the thermal fuse and thermal cut out in a kit. These kits normally solve no-heat problems rather than when the dryer won't start. However, in some models, this kit will solve both problems. Even though this is not the most common part to fail if the dryer won't start, both can be checked using an ohm meter or continuity checker. If they have continuity they are good. If not, they should be replaced.
If the dryer won't start, there might be a belt switch that has failed. This is not a common problem and most dryers do not have this switch. If the dryer has a belt switch, the switch shuts off power to the entire dryer if the belt breaks. It is possible that this switch has failed, even if the belt is not broken. It can be checked with an ohm meter or continuity checker. If the dryer works at all, even if all it does is hum, this is not the problem.
Main Control Board
The main control board is normally not at fault when the dryer won't start. First, check all of the other components in this troubleshooting guide before replacing the main control board. The main control board can not be tested and must be replaced if it is defective. If there are obvious signs of burning or a shorted out component on the board, it should be replaced.
The timer is normally not at fault when the dryer won't start. In many situations where timers are replaced they end up being returned. First, check all of the more common components in this troubleshooting guide before replacing the timer. If the dryer won't start, the cause is much more likely to be a thermal fuse or switch. The timer can not be tested, it must be replaced if it is defective.