A lack of heat to a dryer can be caused by literally a dozen different parts working wrong.
This problem is not easy to diagnose by yourself, unless you get lucky and it's something simple like a blown thermal fuse. We recommend you get a professional to take a look at your dryer; if you insist on troubleshooting at home, get your multimeter ready!
So, it's not the thermal fuse? Check the igniter for continuity. All good? What about the heating element, did that past the test? Now, what about the flame sensor? When using a multimeter to check this, it's imperative to test for continuity when the sensor is at room temperature.
Continuing down the line: if it's none of the above, what about the cycling thermostat? This part is responsible for regulating the temperature and controls when heat turns on and shuts off to keep the temperature controlled. If there's no continuity, there's your problem.
Still unsure what's to blame? Maybe the high limit thermostat isn't working right: give that part a test also and see if it has continuity.
You might also need to use your multimeter on the timer. We suggest you leave this troubleshooting step for the very last as it's one of the most uncommon causes of a dryer with no heat. Further, you must be in-tune with the wiring of your dryer when messing around here.
Troubleshooting your own appliance always seems like a good idea. After all, it can save you on a diagnostics appointment with a dryer repair pro. The problem is you will likely spend hours figuring nothing out and possibly replacing the wrong part. It might be better to just bite the bullet right away and call in a dryer repair professional.
Modern dryers typically feature moisture sensors. These sensors read the dryness level of the clothing and tell the dryer when it's okay to stop the load. This feature is great for energy efficiency as it allows you to avoid running the machine for longer than what's necessary. However, sometimes the sensor becomes defective - a sign of this is a dryer that keeps running even though the clothes are certainly dry. Replacing a sensor is a bit of a hassle without professional help, but the part itself is very affordable.