bristang5

Have a strange issue. I have an oem factory wire harness W/tach. I am adding the fog light wire harness with interrupt to activate the tail lights. I found the hot lead to plug in under the dash and have power in on to the fogs. Now I did get one tail light working at first with the switch. I turned the parking lights on and it went out. Now they will not turn on with the fog light switch at all...I do have my stereo memory powered by the cigarette lighter lead...I can unplug the tail light harness from the head light harness and this seems to interupt the cigarette lighter power...also the hot lead under the dash that powers the fogs also goes off line when I disconnect the tail lights. Any ideas where I check this?

Thanks