94 volvo headlights wont work

I have a 94 volvo 940 gl that i bought off my brother. he tried replacing the radio and instead of buying an adapter kit he spliced the wires and now the headlights no longer work. the running lights are ok but the headlights will not work at all. not sure if the radio deals with the lights or ???. we have checked the switch and fuses and even the relay but no luck. anyone know of anything else?? please help.