Instrument bulb lighting...still dim

My headlight dimmer knob only illuminates my dash lights in a certain position. If I rotate it either way just a 'hair' the instrument lights go out. Its always been like that since I got my '66 Barracuda over 10yrs ago. Also, awhile back I replaced my floor mounted high beam switch and after the install the high beam indicator 'red' light illuminates when its tghe low beam is on and goes off when the high beams are on. This didn't happen with my old switch. Could this interefere with the circuit?