[cknuth]

Just got off the phone with Mark Merritt at Newell. He says that the HWH slides that use magnets to detect the retracted position were originally equipped with magnets under the roof skin of the slide. Everyone who has magnets visible on their roofs has had them added over the years. I just held a small screw near each pin socket, and it stuck to the magnetic spot in each case. So maybe one of my detectors is the problem, or maybe I need to add the stronger external magnets. Will report the results. (also posted this reply in the thread, "What is this, and what does it do?")