I have a Micro-Lite 18FBR. It has a suburban heater and furnace. Initially, I couldn't get it to work last time I had it out, but that was operator error. Working well, now. But I was looking at the thermostat. Not sure how to set it, other than the slider on top for warmer/cooler. What is the "longer cycle" thing that sits on the coil. How does it work? And how should I set it? Also, any suggestion on a digital to replace it with?