How to check the defrost when visually it looks fine.
If you are getting ice impacted on the evaporator coils then you have a defrost failure. You can turn the defrost timer until it clicks which will allow the unit to start the defrost cycle. Wait 15 minutes and if the ice starts melting then the defrost heater and thermostat are working and you will need to replace the timer.
The evaporator has been icing up, first I replaced the defrost timer, 3 weeks later same symptom.The defrost heater had infinite ohms at room temp.The defrost terminate switch, I forgot to check when it was buried in the block of ice.At room temp, 2 of three wires had continuity, one was infinite. Stupidly I now can't remember if it was brown/ orange or white. What is the normal resistance range for a defrost element? I BELIEVE this is the problem, just want to make sure. ....Thanks Rob.
Answer Rob, You should have had 33 to 34 ohms resistance across the defrost heater terminals 63001595, regardless of temperature. If you had infinite resistance (000) then the heater has failed. If you read a "closed" circuit from orange to brown or blue wires, with the thermostat in ice, then the thermostat will be testing "good" and you'll need to replace the heater.