The ignitor detector(flame detect), those coils, and the ignitor are all energized at once. One of them coils has 3 wires to it. the other has 2. The 3 wire coil is also wired to the ignitor to allow current as long as the gas flame is hitting the ignitor. If the flame sensor were to shut down and for some odd reason the gas did not ignite, when the ignitor cooled down it would kill the power to the gas valve. That is the built in safety. Why don't the gas come out when it is energized? Because the resistance in the circuit has to change. It does that by dropping out the ignitor and flame sensor. Then the ignitor takes over as a sorta thermocouple device and allows the whole shebang to stay a going until the power is shut down when the drum air klixon mounted on the blower is satisfied. This cycling continues all throughout the drying process. Them coils get IFFY with age and can fool you. The flame sensor IN RARE CASES will hang up, the ignitor is either going to be good or bad no in between. Replace them coils is what I would do.