The power is fed from the fuse panel to the headlight switch via blue with red striped wire and them to each bulb. Check for power coming out the fuse to the switch then see if the power comes out the switch to the dash bulbs. If it doesn't come out the switch with the lights on then = bad switch. My bet is the rheostat in the switch has a bad contact or the resistor coil is bad in the switch for the dimmer.

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Stu

1967 Mustang Coupe

1964 Mercury Park Lane Breezeway