System is a gas furnace with Heat pump. This system has worked for years with a conventional T stat and outdoor t Stat. The outdoor thermostat was set to 38 deg F. the gas would run under 38, heat pump above 38. I set up my Nest T stat following the instructions but the W2/Aux terminal never has voltage, even in test mode. The old outdoor t stat is disconnected, I programmed the Nest to use W2/aux under 38 deg F.