My refrigerator/freezer is a Frigidaire Model #FRS6HR5JSBO, Serial #4A80805221 (about 14 yrs old). The freezer keeps freezing up and the refrigerator keeps getting warm. I have replaced the thermostat (about 2 weeks ago)and that didn't stop the freezer coils from freezing over. The problem I have is that I can't seems to locate the defrost timer. I have removed the control panel in the refrigerator (not there) I have looked behind it (rear panel, not there). So I'm wondering if this model has an automatic defrost timer and if that just replacing the defrost heater is the solution?? Please help because even though I'm NOT a refrigerator repair man (LOL) I am rather handy and can kinda figure this out.