I had this same issue and it turned out my fuse blew. Some things to check are:


Often a dryer heating element burns out, but doesn't trip the circuit breaker or blow a fuse. The heating element is simply a long coil of special wire. You can check it for continuity with an ohm meter. No continuity means the element is bad and you need to replace it--electric heating elements aren't repairable.


On many dryers, there's a thermal fuse mounted to the exhaust duct inside the back cover panel. The fuse--which is about an inch long--is usually embedded in black resin and mounted in a white plastic housing. If the fuse has blown, you need to replace it. (You can't re-set it.)


A common problem is for the main wiring connection from the house, at the dryer, to burn and break its connection. Because the dryer can still tumble with partial power, the connection may be only partially defective. You may need to replace both the power cord to the dryer and the terminal block inside the dryer that the wire is attached to.

If the flame sensor is open then you won't get any power to the ignitor. The way it works is this thang: bosch dishwasher troubleshoot.pdf (554kb) downloaded 22,624 time(s).mounts onto the side of the burner chamber next to the Ignitor. When this flame sensor is cool it will have continuity and allow for the ignitor to be powered up. So as you dryer is tumbling around and round in the cotton cycle or perma press then the thermostat mounted on the blower vent housing begins to get a cold chill in the air so it clicks on and throws 120 volts to the Flame switch coils and ignitor all at once. All at once you say? If that ignitor ain't on then raw gas will come out and a nasty smell will be present won't it? Nope. Because that ignitor is a voltage hog. It robs the power from the coils so they cannot raise the flood gates. Pretty simple ain't it. So when the control thermdisk powers up the gas assembly the first thing that needs to happen is that flame sensor needs to be cold. If it is warm it will be open. When it is cold it will have continuity. It will ALLOW the ignitor to fire up. That old ignitor get hotter and hotter and hotter till that flame sensor just cannot stand it no more and the bi-metal inside of it shuts off the power to the ignitor. The power to the coils is still on but the ignitor is shut off. A surge of power hits them coils and they snatch up the floodgates allowing the raw gas to enter into the burner chamber and come in contact with the now screaming hot ignitor and Kawhoosh it fires off!. That flame gets the inside of the dryer drum warmer and warmer and warmer. The controling thermostat is judging that air temperature 140 degrees 141 degrees 142 degress 150 degrees and up to 160 degrees,NOW the air is warm enough so is shuts down the power to the gas assembly and the dryer keeps chugging along until the air get cool it drops to 105 degrees then 104 then 103 then 102 then CLICK it fires up the gas assembly. By that time the flame sensor has cooled back down to a point where it has continuity. It allows for the ignitor to come back on. This time it may not take to long for the flame sensor to shut off the ignitor and allow gas to ignite once again. This happens throughout the drying cycle until the timer gets near the end and no longer allows for power to even go to the controling thermostat, this is the cool down portion.