Gas and Oil Home Heating Furnaces - Heater will not shut off when temp is reached

I just installed a lux tx1500 electronic thermostat this summer to cut costs in the utility bill. Everything worked great until know. I am in georgia and the temp is about 45. I turned on the heater for the first time since the installation and when I set the temp I want say, 75, the heater keeps running past it. Last night it never stoped running and it got to 86. So I started reading the directions and tried to swap a wire. I turned off the fuse and swaped it, then turned it back on, and now nothing works. no a/c or heat. I tried auto and on and nothing. So please tell me what I am missing. I have checked the breaker 6 times know and it is on. I tried disconnecting all the wires and reconnecting and still nothing. Please help, it was fine before!!!! I have central heating and air, but of course I did not mark the wires as I took them off, I went by color, but like I said the a/c worked perfectly.

what kind of furnace do you have? gas or electric. if you turn on the fan from auto to on and the fan runs then you haven't shorted the transformer. the wires behind the thermostat may have been nicked when you replaced the tsat last summer.

tienda3:

In most cases the terminal ID on the furnace will match the terminals on the stat.

You should go to the furnace and mark down the terminal ID and wire color and then go to stat and then match the colors to the correct terminal.
Sometimes the air cond is not connected on the terminal strip. That would be the Y terminal on the stat.