I have a '48 Chevy 1/2 ton p.u. I actually have 2 good working turn signal switches (chrome Yankee Turnflex and black Signal-Stat 900), both 7-wire, that I can use. All lights work around the truck as they should. However, on each switch the indicator lights on the faceplate will not work. When tested, each will light up. What's happening here?