I have a 95 grand am, I was installing a new stereo and accidentally cut the wiring harness off, now I have no power to the dome light, and other things on the dash. plus when I connect the new stereo I need to put the ignition 12v AC, and the battery-constant power wires togather that came off the (cut Harness)in order to make the stereo work, and as well as the dash and domelight. But it will also not keep constant power to the stereo.What did I do and how would I go about fixing it?