Heats for a while then stops

First make sure you have good air flow from venting. If you are not sure if the vent is plugged, remove the vent from the back of the dryer. If you run 2-3 cycles and its heating good you have a plugged vent or possibility the outside vent flap may not be opening causing a restricted air flow. If the vent is not the issue, I recommend installing a new set of booster coils on this unit and also checking to make sure you have proper airflow through your dryer exhaust.See parts and video links below.