Ok did some recherch and worked out yes it’s the dimable neg- wire on the 4pin plug. “Dual zone
icc have extra plug on top”
One of the 2 black wires both being -neg one is for the constant clock power the other is for the light. To fix can be easy
-Always full illuminated just joint both black wires
-Do dim with dash find which black one is the dim -neg (with light tester find an earth on body, find the constant clock+ on plug, loop clock + with the black wires, the black that the light won’t turn on with is the dim-) power supply is on cluster pinout 19 light blue red illumination output 25w