Julio B Nrh , TX May 12, 2016 Appliance: Magic Chef Freezer MCUF88W Magic Chef Freezer Mcuf88w: Fridge was not working all it made was a humming noise that would come and go. How to replace Dufm320 Ptc. I bought the start switch along with the O/I protector as I wanted to make sure that was not the problem either. Do-It-Yourself Rating: Repair Time Estimate: 15-30 minutes