this happened to me like a month ago. Try spinning the dimmer switch, its located right below the switch panel to the left of the steering wheel, a small spinning circle stickin a little bit out of the dash.
if its not the dimmer switch and you've checked the fuses id say take the guages out and check everything behind it make sure everything ok back there. (all thought I figure they would be consdiering your gauges work just dont light up)
the fuse is under the drivers side dash in the kick panel.... theres two fuses...one is the GUAGE fuse and thats for the actual functionality of the gauges..the other one which is probably the one yuo want to check is the TAIL fuse....thats hooked up to your lights in youg auges as it turns on the tailights when you put the headlights on at night etc etc.....
my dim lights are just that- dim. In any newer car they are nice and bright. My switch dial is on full but I think the bulbs need replacing or something. I can't even see the oil pressure gauge in the dark.
My cousin had the same problem in his 89 Turbo. None of the guages would light up and it was sad cuz he had just bought a chrome face plate. But anyways, he solved the problem by changing the panel with the 4 buttons, i believe they were the 2 coin holders, defroster and fog lights. Oh by the way, he took that panel off of a 87 non turbo so if you were wondering if it fits, your answer is it does. Hope that helps.
I had that happen in my 89T. Some of the wires had shorted and melted near the radio and shifter assembly. I noticed someone had put a 30amp fuse where a 5 or 7.5amp (memory is a little foggy) was supposed to go. Looked like some circus monkey stereo installation was the original cause, and the fool putting bigger fuses in made it worse. Anyway, I hope that isn't the cause of yours, but I thought I'd just throw that in.