A/C control unit isn't lighting up with the headlights/dash lights.

[TriniTT]

I've owned this '92 coupe for a few months now, and it has an SR swap. Since I've owned it, everything has worked great, but the A/C control unit does not light up when I turn the headlights on. I checked all the fuses and they're all good. I took the unit out and installed another, but still had the same issue. I pulled out the unit, checked the wires, and found one red/yellow stripe wire with a test light that gets power when the headlights are turned on, but the rest do nothing. I also pulled the two tiny bulbs in the top of the unit out to make sure they work, and both bulbs work fine.

Any suggestions as to what on earth could be causing this to not light up would be great. Thanks!