Get your multimeter and check resistance to ground for turn signal wires that are not supposed to be grounded (like the 12V wire.) I would just pull off the cover for the front or rear signal and test between the positive light bulb socket contact and the negative one. Infinite equals good, a moving needle equals bad. If you don't find a problem, move on to the next signal. You probably have a short on the hot wire between your switch and your front or rear signal, which means there will be little resistance between that wire and ground. Good luck.