My dryer will not heat. The flame lights for about 20-30- sec then goes out . If i let it sit for a few minutes and try it again same thing happens. I checked the exhaust duct and it is clear. I checked the temp sw, radiant sensor and hi limit thermostat and they all have continuity. I checked cycling thermostat and it has continuity . I'm not sure how to check the rest of the sw, mine has 5 terminals on it. I tried new coils this time and no help. I also checked the new coils and they checked good. The last thing i notice is when it stopped working it seem that the timmer didnt advance like it normal does. I tried the dryer on didfferent timer settings and no help.