help me solve my problem

[89 coupe]

ok so my cluster illumination lights, heads up display and odometer dont work. and no its not the capacitator thing on my hud because when i turn my key off it will flash. all my gauges work, all my interior, exterior, radio and dashlights work.

ok so heres what i have tried so far.

1. checked all the fuses and there ok2. tried 2 different TCU's (not the problem)3. checked out the wiring and there doesnt seem to be any breaks or anything.4. all the wires coming from the illumination switch to the cluster read 9.1V(should it be 12V? )5. the ground wires have 0 resistance.

dont know if this will help