2001 Ford Mustang Dashboard Backlights Out

Good Morning, I had someone install a Aftermarket Stereo in my Mustang. After installation I noticed that the Dashboard back lights were out. Some of the indicators work, i.E. High Beam, Odometer, I checked all of the fuses under the dash and in the engine compartment. I took it to Best-Buy and had one of their Techs look at it and he had no clue. So any suggestions you might have would be appreciated.