I have a 17 year old Maytag side-by-side refrigerator that had been working with no issue for the nine years we have had it (came with the house) until a few weeks ago when the fridge side was no longer cold. I cleaned out the back of the fridge and blew out all the dust bunnies (it was overdue for sure) and also noticed the evaporator inside the freezer was all iced up. I let it thaw out natually, did a continuity test on the defrost heater and got 20 ohms. From reading online, I thought it may be the automatic defrost control unit so I replaced that with an aftermarket unit. Started the fridge back up and about 3 days later, the evaporator had iced up again. I thawed it out again, tested the defrost heater element again (same resistance values), left the cover off over the evaporator and started the fridge up again. The evaporator blower has been running what seems like non stop since I started it up (maybe because I didn't put the cover on it?) and I can see the evaporator frosting up again. There is no food in the either the fridge or freezer now and I've felt along the door seals and do not feel and cold air plus with no food, there has been little opening and closing reducing the risk of someone leaving the door open a little.
From what I researched, it seems like the issue is the defrost circuit is not working (I can see frost on the defrost heater element currently) and the issue is either the defrost heater and thermostat or the auto defrost control. I replaced the defrost control but maybe that part was bad or despite my resistance test on the heater element, maybe it is still faulty and I should replace it? Could there be something else at fault that I'm missing? I'd prefer to fix this fridge if I can. I realize it's no spring chicken but fixing it if i can would spare me going through the process of getting a new one.
Maytag Mode # MZD2766GEB