Dryer: Why won't my dryer heat?

The gas burner assembly uses solenoid coils in a circuit with the flame sensor to safely ignite the burner. When the dryer starts a heated cycle, the circuit through those components is energized. The igniter glows until it reaches the proper temperature to ignite the gas, at which point the flame sensor trips open and the current flowing through that circuit is diverted to the gas valve coils so the gas valves open, and the burner lights and continues to burn. If the solenoid coils on the gas valves fail, the gas valves won't open for ignition. If the gas valve coils are weak, the burner lights during the initial ignition sequence from a cold start but it fails to light the burner on subsequent ignition attempts. In this situation, replace the valve coils.

The heating element generates the heat needed to dry garments. If the dryer is not heating, check the element for visible damage and replace the heating element if it's broken. Almost all electric heating elements require 240 volts to function correctly; if the heating element won't heat even though it's getting the 240-volt power, replace it even if it doesn't look broken.

The thermal cut-off fuse is a safety device that shuts down the heat source if the dryer severely overheats. The dryer severely overheats if the high-limit thermostat didn't shut off the dryer when the heat source began overheating. You can't reset the thermal cut-off fuse--you must replace it, as well as the failed high-limit thermostat. The thermal cut-off fuse kit contains both components.

The electronic control board governs the timing and execution of dryer functions. The wiring connections on the control board can be repaired, but the control board itself cannot. Replace the electronic control board if it's receiving voltage but isn't transmitting it to the dryer components, causing the dryer to not work. The dryer may start but then stop in the middle of the cycle if internal control board components don't detect sensor signals accurately. It can be difficult to determine if the electronic control board is the problem (unless you see burn marks on it) and it's an expensive part that can't be returned once installed; for that reason, have a trained service technician perform advanced diagnostics on control board before you replace it.

The timer on the control panel lets you set the drying time by turning the timer's control knob. A small motor on the back of the timer advances the timer during the cycle. The timer's internal cams open and close switches or contacts to operate the various electro-mechanical components in the dryer (mainly the drive motor and the heating element). Replace the timer if the contacts aren't working, the dryer won't start, heat or continue running, or the timer won't advance.

The igniter glows white hot at the start of the burner ignition sequence. When it's hot enough to ignite gas, the flame sensor detects the temperature and opens electrically to divert current flow to the gas valve coils. The gas valves open, and the burner lights. If the igniter doesn't get hot enough to trigger the rest of the chain of events, replace the igniter.

The flame sensor detects when the igniter is hot enough to light the gas burner and trips to begin the ignition process in a gas dryer. If the flame sensor doesn't trip, then the burner won't light and the dryer won't heat. Replace the flame sensor if it doesn't trip when the igniter heats to ignition temperature.

The operating thermostat — also called the cycling thermostat — senses the air temperature inside the dryer drum. It controls the heating element in an electric dryer and the burner in a gas dryer, turning that heat source on and off to maintain the temperature at about 150 degrees Fahrenheit for the Normal setting. If the thermostat fails, it won't control the heat source, in which case the dryer might not heat at all or it could overheat. If the operating thermostat is not regulating the dryer heat properly, replace it.

The high-limit safety thermostat shuts off the heat when the dryer overheats because either the operating thermostat fails or the heating element has a short circuit. The safety thermostat resets when the dryer cools. If the safety thermostat fails in the open position, the dryer won't heat. If it fails to trip and shut off the heat, the thermal cut-off fuse blows, to prevent the dryer from seriously overheating.

The thermistor is the dryer's temperature sensor, which is usually mounted on the blower housing. If it doesn't detect temperature properly, replace it. If it has a catastrophic failure and ceases working at all, the dryer usually displays a fault code.

Some dryers have a heater relay that the electronic control board controls. The heater relay controls the heating element in an electric dryer and the gas burner assembly in a gas dryer. If the heater relay fails, the dryer runs but doesn't heat up.

Preventive maintenance for a dryer includes cleaning lint from the vent tube that runs from the dryer to the outdoors. Trapped lint can clog the vent, which creates a fire hazard and can increase drying times.

A clogged vent tube also can cause the dryer to overheat and trip the thermal fuse, causing the dryer to stop.

Check the power cord for damage and replace the cord if you see any break in the wiring insulation.

Clean the outside cabinet and the inside of the drum using a soapy washcloth. Wipe down the surfaces with plain water to remove soap residue.

Wash the lint screen with water and a soft-bristle brush to remove fabric softener residue following the instructions in this video.

The thermal fuse is usually mounted on the blower fan housing. It detects the temperature of the air venting from the dryer to the outdoors and trips if the air becomes too hot. It typically trips if the vent tube is clogged or the exterior damper is closed. In an electric dryer, the thermal fuse shuts off the dryer when it trips. In a gas dryer, it prevents the dryer from heating, but the dryer still runs. The thermal fuse doesn't reset when the dryer cools and must be replaced if it trips.