This has happened to me on two different models. If there is a "cold blast" feature, it may be stuck. Unplug hair dryer and check around the cold blast button for a small screw. With a small screwdriver, loosen the screw only about a 1/4-1/2 turn. This should be enough to loosen up the cold blast button. When I turned my hair dryer on, I had heat once again.

This has happened to me on two different models. If there is a "cold blast" feature, it may be stuck. Unplug hair dryer and check around the cold blast button for a small screw. With a small screwdriver, loosen the screw only about a 1/4-1/2 turn. This should be enough to loosen up the cold blast button. When I turned my hair dryer on, I had heat once again.