I tried to change from our Bryant non programmable termostat (w/ mercury) to a Lux non programmable thermostat (non mercury).

The LUX thermostat did not need as many wires that the Bryant thermostat needed. There was an A screw, but don't know what wire goes on A. There was a jumper between RC & RH and already a yellow wire hooke to the Y screw. We tried to hook the wires we had to the new LUX, but had no luck getting the A/C to come on.

Tried to change back to the Bryant thermostat, but still no luck. We connected the White wire to the "W1" screw, Yellow wire to "Y", Red wire to "R", Orange wire to "O", Green Wire to "G", and Blue wire to "C" screw. I have no idea what we have done wrong to reattach the old thermostat. We get no A/C or Heat blowing.

Did you disconnect the power before changing the thermostat? If not you may have blown the transformer or the 3 or 5 amp fuse on the board if you have one. Do you have a volt meter and know how to use it? If so , we can do testing to pinpoint problem

I didn't turn the power off. I was told to check the fuse box. The heat pump and furnace's switches did not trip. Could I still have a blown fuse, even if they didn't trip in the box? I don't have a volt meter. Can I get one from the hardware store? I have no idea how to use one. Would I use it for the wires or fuses?

Should I just try to connect the wires that make the A/C work and see if that works?

Thanks again.

YOu could connect the red,yellow and green wires that come through the wall at the thermostat. THis would make the inside fan and outdoor unit run if all is well. If it does not work, open the inside unit up and look and see if you have a circuit board on it. If so you will have a3 or 5 amp auto type fuse. It probably blown. If you do not have a board, the transformer is probably blown