My wires have been cut, not by me but a previous user down the line. So having to hunt down a loom, when I eventually find one out of a scrapper will try wiring it up. As for connecting it to an aftermarket stereo, will deffinately buy a harness, if you do get one, dont get a cheap £15 one becuase they are made to a high standard and subs wont work unless you use seperate wiring. Im about to buy one myself.
But if you dont want to buy a harness then you have a loose connection within the wiring causing it to cut out its happened to me on a previous car