Jack beat me to it. Those brake switches in the hand control are downright tiny and fragile. Before opening, or especially reassembling the control housing, you MUST use a spacer to space the hand lever a bit in the 'actuate' direction, so the button on the switch is cleared, or you will most times break or damage the switch.Could be a broken brake light switch or a bad master cylinder also, have you had the lever off recently or done any work to the switch housings? Harley Davidson Community have a look here