Here is a diagram of the dash lights. Power for the lights comes from the headlight switch on the brown wire. It splits @s211 and goes to the dimmer and pin "D" of the dimmer transistor. Power comes out of the transistor on pin "C" and goes through the 5 amp "inst lps" fuse and then on to the lights. The dimming signal comes in to the transistor on pin "B".
If you have power to the transistor on pins "B" and "D" with the headlights on, and the 5 amp fuse is good, your transistor is bad.