The evaporator coil is frosting up. Every six or seven days air flow is restricted to the frigerator side. Its a side by side frigde. I test the heating element for continuity. Passed Test. I tested the t-stat or (bi-metal switch) to see if it is working. It is. I tested these first because i cant find the defrost timer. Any idea where it is at and how i can deductively or inductively test it? I understand the concept of testing a non electronic defrost timer. If i could just find it. The fridge is two years old. thankyou.