The heater is easy to check. Get a meter and look for continuity. If ya aint got a meter get a suicide cord and check it the old fashion way. Remove it from the ice box and bench test it. Put it on a surface that cannot melt and briefly apply power from a wall socket to see if it starts to warm up. Only takes a sec to see if it is gonna heat up. The terminator must be sitting in a freezer under 25f for a few hours. Then it has to be tested quickly for continuity before it warms up to 50f. So you have a very short window to do the checking from freezer to test bench. What that dude does is kill the power to the heater when the frost is melted. Since the defrost control is electronic it could stay in defrost for anywhere from 20 minutes to 40 minutes. You definitely would NOT want the heater to stay on that long.