Gas dryer not heating.

Sounds like broken belt on older models it will not know if the belt breaks and will keep heating and motor running

Kenmore Gas Dryer Model # 110.79722800 timer will not advance in any position dryer work and heats fine just won't turn off when done.

replace igniteor

you have probably lost one leg of your power supply feed 120volts+120volts=240volts,your motor will operate on 120volts, but the element won't,also if you have 240volts the neutral wire to the element can burn off w/heat and age

there is thermostat in the unite look at owner manual that what sounds like. basically it is sensor that tell the unite to turn off.

change the fuse in back of the dryer

Does the motor run? If the answer is no check the door switch. If yes then check the thermostats and thermal fuse.
Eric

No heat at all? does the top of the machine heat up, but not the drum? could be your drum seal is damaged or slipped off.
If the firebox doesn't light up, could be your igniter, the unit's safety switch, thermocouple, or regulator; Your Gas Company may provide a service that would check it for you... some do.

Try replacing the valve coils first, then the valve if the prior doesn't work. If there is a buzzing noise, I believe it's more likely the valve. I'm replacing both on mine to be sure.

check rear tub rollers and also check the idler pulley