Did i do this wrong? Cause i think i did.

I removed the old mecury thermostat and connected a new electronic thermostat. When i turned it to heat it would heat the house to the desired temp and the heat would turn off but the fan would stay on and continue to blow cool air indefinately .

I ended up exchanging it for another one and the new one is causing the same problem making me think that i wired this thing up incorrectly.

ETA: the angle on that photo sucks, but the blue colored wire is hooked up to the B terminal not the C terminal.

I'm not an expert, actually I know next to nothing regarding HVAC, but when I replaced my thermostat I popped the cover off my furnace to make sure the wires were marked the same on the furnace end as on the thermostat end.

IIRC I did that in part due to my old thermostat being a very basic heat only that had less connections than the new one which is still basic but has the ability to do AC as well as heat (although I only have a furnace, no central AC) and the wiring has more wires than I needed to connect, I guess when they ran it they put the max number of wires you might be able to use so that the wiring wouldn't have to be rerun at a later date

Bump for exposure

Look in the furnasty and see what the blue wire lands on in there. It may be the c for common. The rest look fine.

I did just this and what i discovered was that the blue wire was on G. I just rewired the thermostT and it works perfectly now.

Thanks guys!