I just installed a new blower to unit outside, I was checking the wires on the power relay to make sure everything was good and tight, when I seen a spark and the A/C stopped working. I tested the power from the house and I was getting good juice but when I went inside I have no power on the thermstat. I order a new power relay and plugged the wires in just like the old one, and still no power on the thermstats. I have checked and reset all breakers and still no power. Does anyone have any ideas on what I could have done. I do have power from to the unit outside 120v, and the handler but no power to the thermstat and the unit will not work at all.
Thanks in advance

Unless you have a real small outside condensing unit, you should have 230 volts to it. If you don't have power to your thermostat you most likely have blown a 24 volt fuse off the transformer. Depending on the make, model and age, it could look like a automotive plastic type plug in fuse or it could be a small glass cartridge fuse.