96 Caravan elec. problem

i have an issue with the right turn signal it seems to work fine that is until you turn headlights on. when the lights are on the signals still seem to be working fine until the brake pedal is depressed then the right signal only starts speeding up significantly quicker. the only thing that comes to mind is that maybe current being supplied to brake light is also being supplied to signal but there is no way for me to be sure ( no schematic ) any input on this issue would be greatly appreciated. Thanks