I have a 1943 Chevy Fire Truck 6 volt system. I have headlights, running lights when the headlights are on and brake lights. I cant get the flashers/blinkers to work on either the front or the rear of the truck. The rear lights are a two light bulb system (one for brakes and for flashers). Any ideas on where to start checking? Could the blinker switch possibly be the problem? How can I check? Thanks