As another reviewer mentioned, the polarity of the controller outputs is reversed. I only checked because I read this review. The reality is that most soldering irons have two-pronged ungrounded plugs, so it probably doesn't matter much. But since my soldering iron was handy I went ahead and fixed it. Swapped two white wires and that's it. Literally a 5 minute fix. Otherwise the controller basically works. Since this is a simple rheostat and not a temperature controller, finding a middle ground