My Masterbuilt smoker control unit is always displaying 300 degrees. I took the control unit apart to inspect for any dirt or corrosion, but it still looks brand new. I cleaned the area around both the sensors inside and dried it off with hair dryer but that didn't help. I see screws on the inside to take out the sensors, but I don't see how to take the back panel off to remove the sensors. The back panel appears riveted on. I live in Florida and it's only 55 F, so it's not an outside temperature issue.