Kenmore series 90 Model 11074902200… Dryer starts normally and heats up within a minutes but as cycle progresses it becomes cold and intermittently warms through out heating cycle. Even in a full dry cycle, clothes does not completely dry. I replaced heat selector switch with no change in problem. wondering how to pin point problem before i start ordering new thermostats, thermal fuse, and thermal cut off.
I do very little work with the gas heating components of gas dryers, and your problem sounds like a problem with your gas firing system, probably the coils.
Search this site for gas dryer coil problems and see if you cannot find some discussion which fits your problem.