My 10 year old Amana Side by Side (Model SRD 20S4 E - P1190810W E) does not get the freezer cold enough, only about 25 degrees. The refrigerator is a little warm also. The fan runs continuosly in the freezer compartment, but there is not that much ice buildup on the coils. Hoping for an easy fix, I checked the defrost heater - it is ok and I replaced the defrost thermostat (although the old one did check good when I had a chance to stick it in another freezer later). I could not find the defrost timer. Is there a defrost timer on this model? What else could be the problem?