I had ice building up at the bottom of the fridge under fruits and vege baskets.I The draining hole was clugged and i cleaned it up but the problems remained. I called a repairer who changed the thermostat. It looked OK for a while (one week) Now ice is building up on the back wall on the top of the fridge and someone told me it i should change the defrost timer. Where could I get one and where is the defrost timer located? Regards Bernie