My dryer is not heating properly. I have cleaned all the venting (taken dryer apart to do so), I have replaced the ignitor, and both coils on top of the valve. When I first turn it on, you can see the ignitor illuminate, then you can hear the flame begin. It runs for about 10 to 12 seconds, then shuts off. I don't know what else to look for. I assume it continues to cycle like this throughout, but have not sat next to it long enough to verrify it. Could there be a way to test a thermostat to see if it is causing the problem? I have to run the dryer 3 times in order to dry the clothes.