If your dryer is not heating, check airflow before anything else. Clean the lint screen, then run the dryer and step outside: you should feel a strong, warm flow at the exterior vent. Weak flow means a clogged vent, and a clogged vent also blows thermal fuses. If airflow is strong and the drum stays cold, the element, igniter, or a safety fuse needs testing.
This is the single most common laundry call we get, and our dryer repair page covers the service side. The good news: most no-heat dryers are repaired the same day once the real cause is found.
