I have checked continuity on all heater components - thermal fuse, heating element, high limit thermostat, dryer door switch, cycling thermostat. All test OK with ohmmeter. When I removed the temp selector switch (low/medium/high) it appears to be switching OK. With the switch out of the circuit, the element is powered and hot air is produced (very hot), when I plugged switch in again - no power to element, but other functions work - timer switch, blower motor, etc. Is this selector switch defective or is it something else in the circuit? Logically, I must be missing something.

Thank you for your reply. I checked the continuity of the selector switch and found it to be good. The next item down the line was the timer switch. I replaced the TIMER WPW10186032. While a rare fail, replacing this Timer appears to have solved the riddle. No way to easily check operation of the TIMER, but dryer now heats up on each selector switch setting. I took the opportunity to replace vent connection and clean dryer vent line thoroughly. Runs much better.