I am doing final assembly on our 69 Mach 1, here is the issue, 4 way flashers work fine, signal lights do nothing. I can jumper the pins on the harness (Dash side) and make them all work fine, when I hook up the harness going to the steering column, they do not. I have replaced the signal switch with a use one with the same results. Is there a way to test the signal switch? Also I do not entirely understand the signal system. The flashers have power on both sides of them. Seems like the signal switch is faulty, but, alot of work to replace again. Possible the used one I put in is bad.