How long does it take for an average laundry load to dry? Provided you’re using an electric or gas dryer to do the job as opposed to a clothesline, you can expect your clothes, towels, or linens to be thoroughly dry in about 60 minutes. That’s enough time to bake a pie, watch the season finale of your favorite TV drama, or agonize over how you’re even going to begin to clean out the garage.
But if your dryer refuses to cooperate with your plans and keeps shutting off, it’s going to take considerably longer for that load to dry. Before we examine the probable reasons why that convenient appliance has become a nuisance, let’s review how gas and electric dryers do what they do.
How a gas dryer works
Gas dryer models use a burner assembly consisting of an igniter, gas valve solenoids, and a burner tube to heat the air that dries the laundry tumbling in the rotating drum. The burner assembly is energized by a standard 120 volts of alternating current when the timer and heat setting are selected on the dryer control panel and the start switch is activated. The voltage passes through a cycling thermostat, a high-limit thermostat, and a thermal fuse, if applicable to the model, on its way to the burner assembly.
The voltage then travels through a flame sensor and an initial gas valve coil before reaching the igniter. The igniter will begin to glow, and when it gets hot enough, the flame sensor will detect the heat and switch off, which diverts the current to other gas valve coils. The coils then activate plungers in the gas valve which allows gas to flow out into the burner housing. Since this happens very quickly, the igniter is still hot enough to ignite the gas into a flame to heat the air being drawn through the dryer drum.
To maintain the proper air temperature during a drying cycle, the heat level in the blower housing is monitored by the cycling thermostat. During normal operation, the air temperature should be between 120 and 160 degrees Fahrenheit. When the air reaches the proper temperature for your dryer, the contacts in the cycling thermostat will open which switches off the voltage to the burner assembly. When the air temperature begins to cool, the contacts in the cycling thermostat will close, allowing voltage to travel to the burner assembly to reignite the gas supply to heat the air.
How an electric dryer works
Electric dryer models use a heating element to heat the air instead of a burner assembly. The heating element is activated when it receives 240 volts of alternating current through two legs of voltage, each carry 120 volts. The timer, heat selector, and start switch on the dryer control panel allow the first leg of voltage to carry the current to the motor, and through the cycling thermostat, high-limit thermostat, and thermal cut-off fuse on its way to the heating element. The second leg of voltage carries the current through a switch on the motor which closes when the motor is running. The current is then sent to the opposite side of the element. Once both legs of voltage reach the element, the circuit is closed, and the element begins to heat the air.
Just like with gas dryers, the cycling thermostat will monitor the air temperature in the blower housing. When the proper temperature is reached, the thermostat will shut off voltage to the heating element. The high-limit thermostat and thermal cut-off fuse will also monitor the temperature of the element and its housing to ensure the dryer doesn’t overheat. If the air temperature begins to cool, the contacts in the cycling thermostat will close, allowing voltage to reach the heating element which turns back on to warm the air.
Top reasons why the dryer is shutting off
So why would a gas or electric dryer keep shutting off? A dryer can unexpectedly turn off altogether or the heating can “shut off”, or be interrupted, as well. Here are the top reasons why:
- Air flow problem – Poor air flow is the one predominant reason the dryer’s heating will be interrupted. For gas dryers, poor air flow can result in the flame not being pulled through the burner housing in an adequate manner. This can cause the high-limit thermostat to heat up and switch off the voltage to the burner assembly to prevent damage to the appliance. The thermostat will reset after it cools, but the drying cycle may continue to be interrupted if the voltage to the burner assembly is repeatedly shut off by the over-heated thermostat. Similarly, poor air flow can cause an electric dryer to overheat as well, which can result in the high-limit thermostat shutting off the first leg of voltage to prevent damage to the dryer, interrupting the heating circuit. If the air flow problem is not corrected, the thermal cut-off fuse on the heater or burner housing will probably blow and the dryer will cease to heat altogether. If the dryer has a thermal cut-off fuse located on the blower housing as well, that fuse could blow resulting in the dryer not heating or running at all. While you should always clean out the dryer’s lint filter after every load to improve air flow, it is strongly recommended that the entire length of venting be cleaned out with a vent brush, and the vent housing be cleaned with a vacuum, at least once a year.
- Defective gas valve solenoid coils – A gas dryer’s gas valve solenoid coil can fail several minutes into the drying process, shutting off the heating prematurely. If you observe the igniter glowing and then cooling down without establishing a flame, then one or more of the gas valve coils have probably failed. You can use a multimeter to test the coils for Ohms of resistance to help determine if the component is faulty. A properly-functioning two-terminal coil should have a resistance between 1,000 and 2,000 Ohms; a three-terminal coil should have a resistance between 300 and 2,000 Ohms.
- Faulty heating element – If an electric dryer’s heating element is faulty, it may cease to function when the dryer is running. You can use a multimeter to test the element for electrical continuity – a continuous electrical path present in the part. If the meter indicates the element has no continuity, you will need to replace element with a new one.
- Malfunctioning moisture sensor – Dryers will often have a moisture sensor to help detect when the laundry load has been thoroughly dried. A malfunctioning moisture sensor, or one coated with fabric softener oil, may signal the dryer to shut off prematurely.
- Faulty thermostat – If either the high-limit thermostat or the cycling thermostat is faulty, the voltage to the burner assembly or the heating element may be interrupted. Again, you can use a multimeter to test each thermostat for electrical continuity to help determine if either component has failed or not. Keep in mind, since a cycling thermostat is actuated by heat, it should display continuity at room temperature, but switch off, or display no continuity when heated. The contacts in a malfunctioning cycling thermostat may keep opening prematurely, shutting off the heat before the air has reached the proper drying temperature.
Other potential causes of the dryer shutting off
A dryer continuing to shut off could also be caused by an electrical problem in the home. By setting a multimeter to “Volts AC”, you can test the wall outlet the dryer’s power cord is plugged into to confirm its providing the proper voltage. You can also test the power cord itself to learn if the part is defective. The dryer will also shut off if the breaker for the electrical circuit the dryer is on has tripped. Does your gas or electric dryer keep tripping its circuit breaker? These are the four most likely causes:
- Shorted heating element – For electric dryers, the heating element can short out against its housing which can cause a circuit breaker to trip. Contact one multimeter probe to one of the heating element’s terminals and the other probe to the housing or casing. If the multimeter display indicates electrical continuity between either of the terminals and the casing, then the element has shorted.
- Shorted drive motor – A drive motor in both electric and gas dryers can short out internally as well, causing a breaker to trip. To identify a short, use the multimeter to test for electrical continuity between the motor’s power supply terminals and frame.
- Damaged terminal block – Electric dryer power cord wires attach to the dryer at a terminal block. Loose wires can arc and destroy part of the block which could result in a wire shorting against the dryer cabinet and causing the circuit breaker to trip. You should confirm all wires are secured under the washers, nuts, or screws, and replace a damaged terminal block with a new one if necessary.
- Weak circuit breaker – It may not always be the dryer’s fault. Over time, circuit breakers can weaken and may trip often even the amperage is below an acceptable limit. If you’ve already confirmed the potentially defective dryer components are working properly, consider having a licensed electrician replace the circuit breaker.
Prevent your dryer from shutting off with the right part from Repair Clinic
Whether you need a new thermal fuse, cycling thermostat, high-limit thermostat, heating element, gas valve solenoid, moisture sensor, or terminal block to keep your dryer running, Repair Clinic.com will help you locate the exact part that fits your model, including those manufactured by Whirlpool, Electrolux, Kenmore, GE, Maytag, LG, and Samsung. Type the full model number of the dryer in the Repair Clinic website search bar for a complete list of genuine manufacturer replacement parts compatible with your appliance. You can then use the “Part Category” filter (“Gas Burner & Control Valve”) followed by the “Part Title” filter (“Gas Valve Solenoid”) to identify the specific part you need. In addition to millions of replacement parts, Repair Clinic also has thousands of “how-to” videos, diagrams, and articles to assist you in taking on the repair yourself.