Fridge cuts off

Thank-you for your assistance…I have a Whirlpool side-by-side: model number…ED25COQFB02. Problem: It will completely stop cooling/freezing till I turn the temp dial off, and then back on. It will run perfectly fine for a day or 2, sometimes just a few hours (cooling/freezing) then will shut down again. I was told it was most likely the "defrost timer" needed replacing. Thought it best to get a professional opinion before I order any parts. Thanks again…Dale