Headlight swap

[bluesphere]

So the headlights on my series 78 are either the worst headlights ever or im getting old and my night vision sucks. Either way i purchased some LED headlights and can only get them to work on either hi, or low. If I flick the hi/lowbeam switch one side just turns off. I take it there is some kind of property relay. Does anyone know a work around?