Gas dryers are fairly simple. There are four basic areas of dryers you need to understand to know how they work:

- Control panel
- Door switch and interior light
- Drive motor and related parts
- Burner assembly and related parts

Control panel:
The control panel has two or more of the following components:

- Timer: The timer is usually the largest dial on the main control panel. It may be a mechanical device much like a simple clock, or it may be completely electronic with just a digital readout. The timer runs in a pre-determined pattern by sending electricity to each dryer component at the correct time for the correct amount of time.

- Start switch: After you set the timer to the proper cycle, you press or turn the Start switch to begin the cycle. The dryer shouldn't run until you do this.

- Selector switches or knobs: Most dryers have one or more other switches or knobs on the control panel. They let you adjust certain settings of the dryer such as heating temperature, end-of-cycle signal, timer cycle and so on.

The door switch and interior light:
There's usually a door switch inside the main cabinet of the dryer. Look for a button or small lever protruding from the main cabinet on or near the dryer door frame. When you close the dryer door, it contacts this button or lever, which activates the switch and lets the dryer operate when it's started.

When you open the door, the switch interrupts the power to most of the dryer's internal components and turns on the interior light if there is one.

Warning: If the dryer doesn't stop when you open the door, don't use the dryer! If you use a dryer that has a defective door-switch, serious injury to yourself, children, pets, or other people or animals may result.

The door switch and interior light:
There's usually a door switch inside the main cabinet of the dryer. Look for a button or small lever protruding from the main cabinet on or near the dryer door frame. When you close the dryer door, it contacts this button or lever, which activates the switch and lets the dryer operate when it's started.

When you open the door, the switch interrupts the power to most of the dryer's internal components and turns on the interior light if there is one.

Warning: If the dryer doesn't stop when you open the door, don't use the dryer! If you use a dryer that has a defective door-switch, serious injury to yourself, children, pets, or other people or animals may result.

The drive motor and related parts:
Your dryer motor serves three main functions:

- The drive belt attached on one side of the motor turns the drum.
- The fan blade attached to the other side of the motor draws warm air through the drum and pushes it out the exhaust vent.
- The motor prevents heat from turning on if the motor doesn't reach its proper operating speed.

The burner assembly and related parts:
In a gas dryer, the burner assembly consists of the gas valve, the igniter and sensor, and the thermostats. Gas supplied to the appliance is turned on and off by the gas valve, as follows:

First, when you close the dryer door, set the timer, and press or turn the Start button, the motor starts. When it reaches full speed, which takes about a second, a switch on the motor turns on. This allows electricity to flow through a simple thermostat to one side of the gas valve.

The gas valve then sends power to the igniter, which glows bright orange.

As heat and light from the igniter warm up, a sensor next to the igniter causes the sensor circuit to open. This supplies power to the other side of the gas valve and completes the circuit and opens the valve.

Once the valve opens, gas rushes out and the igniter ignites it. As gas burns, it keeps the sensor warm, which keeps gas flowing.

When the dryer reaches a pre-set drying temperature, a simple thermostat turns off the flow of electricity to the gas valve and turns off the gas.

When the temperature in the dryer falls 20 to 30 degrees, the thermostat again allows electricity to flow through to the gas valve, and the cycle starts over.

In an electric dryer, the burner assembly consists of a heating element and one or more thermostats. Electricity supplied to the heating element is turned on and off by the timer, as follows:

First, when you close the dryer door, set the timer, and press or turn the start switch, the motor starts. When it reaches full speed in about a second, a switch on the motor turns on. This allows electricity to flow to the heating element through a thermostat.

The heating element then glows red hot. Air from the blower the flows over the element, through the drum and out the exhaust vent.

When the dryer reaches a pre-set drying temperature, a thermostat turns off the flow of electricity to the heating element.

When the temperature in the dryer falls 20 to 30 degrees, the thermostat turns on the power to the heating element again and the cycle starts over.

For more about dryers, including troubleshooting information, maintenance tips and detailed appliance diagrams of common types of gas and electric dryers, visit our dryer repair help area.