I have a gas furnace with only 2 wires running to a mechanical thermostat. When heat is off, Voltage is about 25 volts AC mesured at thermostat. When heat is on, voltage measured at thermostat is 0 volts AC. Need to know if I can replace old mechanical thermostat with White Rodgers 1F80-261 Thermostat (Digital Programable) and where to attach the 2 wires to the White Rodgers T-Stat. :eek: