First I replaced the defrost timer because I read this was a likely culprit. I didn't have a multimeter to test. After a week the problem re-surfaced. I researched further and found that if the Defrost Limiter Thermostat was exploded that it was probably bad. By exploded I mean that the seals on either end were uneven and burst. I replaced the thermostat and it looks like the problem is solved!