Instruments lights 2

[chiccokaiser]

I have a '95 5.2l model and my instruments cluster lights turn off when I turn on the headlights.
I found out the problem in a card under the steering wheel that has a red plug with a black wire (ground?), a wire coming from the sliding switch that adjusts the brightness of the int. lights (it works), a yellow/pink one that has 12v dc when I turn on the headlights, and an orange one that seems to go to all the bulbs behind the instrumens that now don't work and this does never have power.
I am thinking to drive a n/o rele coil with the yellow/pink and negative so that it will excite it when the headlights will are on, then go trough the contact of the rele with the orange to the positive. Like this I loose the possibility to adjust the lights but at least they will work, dont' you think?
Thanks