The glowbar can fail and mess up the whole works. Or the high limit will kick out due to venting problemas. The flame sensor
a flame sensor 2.bmp if it is open will not allow for the glowbar to fire up thus no heat lets see what else. oh yeah the controling thermostat mounted near the vent blower will die and that will not allow for power to get to the gas valve assembly. If it work some and then not at all them coils need changing. An old school simple way to check the heater/gasvalve assembly is as follows: Warning this is dangerous but what ain't. What you do is get the wife or a friend to be a witness Oops I mean to assist. remove the 2 wires going to the flame sensor hold them apart and have your friend start the dryer on the heat cycle. touch them 2 wire together and see if that glowbar comes on,wait 5 seconds and seperate the wires. the gas should ignite. if it does then your flame sensor is bad.replace that. If that glowthingy don't light up at all then you are not getting 120 volts to them 2 wire or the ignitor is bad. That ought to be enough to git ye started or killed HaHa Just kidding. LOL Be careful . any question just ask away.