So my furnace isn't blowing hot air, more cold than luke warm even. My Furnace is old, like 70's cast iron, but the compatibility apparently is good according to the nest website. I have had this thermostat since this past summer and the ac worked flawlessly. I confirmed the pilot light is on and I THINK the wiring is correct. Using 4/5 wires with the blue disconnected cause it was in the furnace. R/r y/y w/c g/g
