Did you pull the plug and actually look at the pins, or just wiggle it and call it good? I ask because I learned that lesson the hard way on a deice controller last winter. The plug looked fine from the outside, but when I pulled it, two pins had that green crust on them. Cleaned them up with contact cleaner and a little brush, plugged it back in, and the unit fired right up. Saved us from ordering a part we didn't need. Now pulling and eyeballing the plug is the first thing I do before I even think about swapping a box.