T. I have a GE Ambassador Mark II from the early 80s (still going strong). I was installing an Ecobee3 and ran into the C-wire issue. Blue C-wire is there, but not hooked up to the furnace. Please see www.diychatroom.com
Can I use the T terminal in my furnace as the C for a Wifi Thermostat? . diy.stackexchange.com
Installing Wiser Air thermostat where there was no C wire prior . Thermostatic Controls - Installing Wiser Air thermostat where there was no C wire prior - Hi from San Diego, where we really shouldn't be asking about heating nor AC, because we generally don't need www.doityourself.com
