On the first of these two refrigerators, I double checked the instructions that came with the board but still ended up with a frost up again. On the second, another company had been there already and replaced the board. Had the customer not have told me that, I would have been changing the board again. Assuming intermittent failure somewhere else, I changed the bi metal and checked the harness plug. I did a live check of heater and replaced it anyway as they fail often.