The first thing we must determine is the type of dryer we are servicing. There are only two types; Gas or electric.
If your dryer is electric, meaning it uses electricity instead of flame to produce heat, step one is to verify that the breaker to the dryer's electrical circuit is fully on. Since electric dryers require 240 volts to run, their circuit is run through a dual breaker switch. Sometimes only one half of the breaker switch will be off or fail which will supply enough power to make your dryer tumble but not enough for it to produce heat. Pop the breaker to your dryer off and on again and then see if the dryer will now produce heat. If it does, then have the breaker replaced. If it doesn't, you can verify that the dryer outlet is fully powered by testing it with a volt meter, You can learn how to use a volt meter here. If the outlet is fully powered then the problem definitely rests within the dryer.
Let's next deal with the failure common to both types.
You will need a continuity tester for this process.
After you have removed the power from your dryer and shut off the gas, you will also need to access the internal workings of your dryer. Directions for achieving access, specific to your brand, can be found here.
Most dryers have a thermal fuse located in the exhaust path. Depending on your dryer, the fuse will be found toward the front or the rear of your unit. Generally, if there is a removable back on your dryer then that is where you will find the fuse.
The two most commons thermal fuses you might find are shown in Figure 1. They are each roughly 1" in size. You will notice that the contact points are easily spotted for a continuity test.
In older units and some electrically heated units you will find a series of thermal fuses, looking like small tin cans, at various points along the heater assembly. These will also need to be tested before you can rule out thermal fuses as your problem. If any of the thermal fuses fails the continuity test, then it needs to be replaced. You can find reputable parts dealers at the top of this page.
After proving your thermal fuse(s) is/are good in your electric dryer it is time to move on to the next most likely possibility, the heating element. A typical heating element is shown in Figure 2. The element, as are all dryer electric heating elements, is comprised of metal coils supported on a framework with two contact points where wires are connected to the rest of the dryer. A break in this coil will stop the dryer from being able to create heat. Test the two contacts for continuity. If they fail, then you need a new heating element. You can find a diagram showing where each brand tends to place its heating elements here.
If both the thermal fuse and the element show continuity it is time to call a professional to service your electric dryer.
Gas dryers use a burner system to create heat. This system has a number of parts that are known to fail over time. Some you can test, some you must simply rely on symptomology to form your decision to replace or not to replace.
In Figure 3 you can see an entire burner assembly with the various parts labeled. Not all of these parts can be tested with a simple continuity tester. An ohm meter is now required to find your problem part. Directions on how to use an Ohm meter can be found here
The parts prone to failure in your burner assembly are:
- Flame sensor
A burner operates in a fairly simple way. Once the motor is turning, centrifugal force closes the Motor Switch allowing the electricity to reach the Flame Sensor. The Flame Sensor allows the electricity to reach the Igniter, allowing it to heat up to a temperature high enough to ignite natural gas. Once the Igniter is hot enough the Flame Sensor breaks the Igniter circuit which allows the electricity to run through the Coils that open the gas valve. Gas then flows out past the Igniter and catches fire and the heat is drawn into the airflow within the dryer.