Gas dryer will not heat

I need of assistance: My gas dryer operates normally but will not heat. I have replaced the thermostat but this dos not seem to be the problem. Please Help !!!

Which thermostat and for what reason?

Open this diagram. Remove #39 plug, start the dryer on TIMED DRY and look through the hole. Give it about 20 seconds, does the igniter glow?

If it does, replace the coils (see below). If it does not, could be a bad flame sensor, burnt igniter, or bad thermal fuse. All can be checked with an ohmmeter for continuity.