Glad you solved it. To answer your question, for future reference, you can test the S1 like any other switch. Place your multimeter in 'beep' or continuity test mode. If you don't have that, set it to resistance, lowest range, and look for near-zero ohms. Connect one lead to a pole common, and then exercise the switch. The non-common terminals should beep when the circuit completes. The problem with an S1 is it's difficult to know which terminals are which. Here's my diagram once more: The gray square that is the S-1... for clarity I didn't place it atop the pot, but it's oriented correctly. So, the side of the S1 that has the three pot terminals, that's the right side of the S-1, as shown from upside-down, soldering position. You can see there are four poles. It's a 4PDT (four pole double throw) switch. It has the ability to switch four different things, two ways each. Each pole is on a side of the S1. Even though the physical device is cylindrical, the terminals are laid out square, as shown. The four center terminals (green here) are the commons. The ones drawn in pink are the UP or disengaged position. And blue for down. Note the layout is weirdly asymmetrical. Hope this helps.