I have tried swapping out my old honeywell thermo with a new hneywell therm. I could get the heater to work but no ac, then move things around and ac to work but no heat. Then I touched the black and red wires and the sparked a couple time and eventually I realized nothing comes on now.

1. Is it possible that I fried the ac and heater?
2. Could I have fried/ruined the wiring in the walls?

Any thoughts before I dish out hundreds of dollars for an electrician?

Thank you very much for any advice. I am really concerned that I destroyed the actual units, is that possible? I have checked the breakers and they are fine, I flip them on and off.

If you furnace is less than 5 or 6 years old you will have a small fuse on the circuit board of the furnace. It will probably be a 3 or 5 amp. It is the same as an automobile fuse. Find it and replace it. Then wire you thermostat the right way.

If you don't have a fuse, you could have fried the 24 volt transformer. They are less than $20. I would add an inline fuse in that case. As for wiring the thermostat, see the sticky at the top of the forum. You may have to check what the black wire is connected to at the furnace or air handler.