Same thing happened to ours...I found the problem was one of the thermostats. Do you use a lot of dryer sheets? If so, check your lint filter...even though the lint is gone, the filter will have this waxy type build up from the dryer sheets and this causes the dryer to overheat (trip the thermostat) and not heat.
Found it on the back, took it out and gave it a good whack on the ground and it reset...dryer works like a champ now and we clean the lint filter at least once a month with a fine wire brush.
Actually the dryer is close to 20 years old and this was the first service call.
We clean filter each time we use the dryer.
The service guy did check the exhaust and there was not problem (it only runs about 2 feet straight to a hole in the wall so it is not like there is a lot of places for it to get clogged.
No, I think the part just gave out.
It has been two years since the service call and it works fine. I just know when it breaks again we will be getting a new washer dryer, just not from sears.