1993 Volvo 240 Head Lights

I have a 1993 Volvo 240 sedan that will not burn the dim headlights. I have replaced the dash switch, the turn signal head lamp dimmer switch & the head lamp relay switch. So far I have the same problem I started with no lights unless I hold the bright switch on while I drive. This is a starnge problem & I was hoping someone somewhere may have had the same problems? Blroland