Gas dryer will heat sometimes and not heat other times kenmore model 72802

Sounds like bad gas coils,you have to send the whole model number,it will start with 110. or similar,if the bottom panel comes off,remove it,start the dryer, or in the front panel down near the bottom pop off the cover and look in,if the flame lights and then after 10 to 20 minutes the flame doesn't light you have bad gas coils.when the coils are starting to fail they will work correctly until they heat up and then they won't work until they cool down,the coils are what opens the gas valve.the coils are on top of the gas valve,remove the two phillips screws,pull off the cover,remove the wires from the coils and install the new coils,put it back together and you'll be fine,also while you're in there,get a shop vac and vac out the cabinet,stick it on blow and blow all the lint off of the motor and out of the gas tube,then clean out the duct that the lint filter slides into.if your vent line is a long run from the back of the dryer to the outside,i use a leaf blower remove the vent line from the back of the dryer and blow all the lint outside out of the line,do this once a year,you won't have any fires,your clothes will dry on time and your motor and parts will last longer