I have disassembled my dryer, and removed a blanket of lint throughout the bottom portion of the unit. I cleared and vacuumed all vents and throughout the machine and get excellent airflow. When I test the machine by putting it on a heated setting and then starting the machine, the ignitor glows brightly after about 45 seconds, then goes off after about 15 seconds. The burner never ignites, and no gas is noticeable to my nose. I have confirmed the gas supply. Do you think it is the flame sensor, or the coils? Do I need to do continuity testing, if so, how?, or do I have enough information to make a call?