If you look at any wiring diagram for an air handler, like the one linked here, you will find that the only difference between wiring to the C and ground of the air handler is about 8" of wire. Thats because all C terminals in furnaces and air handlers are run to ground. There are alot of air handlers out there with no C term but sometimes a blue wire. Do what works best for you or what you have to work with Here is a link that might be useful: Comformaker Wiring diagram

I climb up the attic open the door at furnace and find out there is a transformer that step down 120 v to 24 v . and two terminals at the second end (24v) red terminal is power 24v and the other terminal is use to connect to frame or chassis and serve as common ground so a c wire is any unused wire you can pick any color you want in the same bundle that goes from the furnace to the thermostat in my case those extra wires are trim flush to the bundle jacket on both end so I need to peel that jacket off about 2 inches on both end and connect a single wire about 2 foot long from the frame to the wire you selected (let say black) on the furnace end then the black wire on the thermostat end will be "C" wire and connect it to the "C" terminal on the new wifi fancy Honeywell or Nest. If I say anything wrong please correct me. I will do this at some other time. for now I just thinking. I signed up for smart (something) at gapower.com and they will sent me a nest gen.3 for free. I think this nest also will need "C" wire. I wait till I get the Nest then I will install both the Nest and the Honeywell at same time I will put the Nest down stair and Honeywell up stair.

turns out the plastic thermometer is reading low so my thermometer is closer than I thought.. So as long as the wires are correct, which another forum said they were then the thing to do is try to ignore the numbers and just heats to be comfortable.. A flannel shirt is always welcome in the winter and sometimes even a sweater to keep the bill at bay.

In a two wire thermostat which is controlling heat only, the connections are 24 V power (R) and heat (W). When the thermostat calls for heat, the W terminal is energized to 24 V. You have to trace the red and white wires to seen how they are connected in the boiler. I would think the red wire is the R connection, and the white wire is the W connection, but that is not guaranteed. The terminals in the picture make no sense since nothing is connected to W, and there is a connection to Y which is normally used for cooling. I am not sure the purpose of this connector. Do you have an AC controlled by another thermostat? Does the Honeywell thermostat you purchased have WiFi? If it goes then you need a ground connection. There should be a ground on the furnace control board. Once you find it you will have to run a wire up to the thermostat.