This switch is supposed to have 5 wires coming from it, one pair to the cut end of each high beam wire and one hot wire for power. There is no ground wire. The fact that you have only 3 wires coming out of yours tells me that someone used it as just an alternating flasher to power a pair of lights, perhaps grill or back shelf. If you want it to operate properly with highbeams you'll have to add back the 2 missing wires as shown in the wiring diagram.
I am using this switch box to alternate red/blue lights behind my grille. How would I wire/connect this to two grille lights?