1995 GMC Sierra Speedometer Lignt and Parking Lights not Wo

My son has a 95 GMC Sierra 1500 Pickup. A few days ago, the light in the dash that illuminates the speedometer quit working. I have checked all the fuses (to be sure I wasn't misinterpreting the description of each fuse) and the (position of the) scroll switch that controls the brightness of the dash. In trying to figure out what was wrong, I also noticed that the parking lights are not working either. I don't have any reason to think the two are related, except that, in researching this, I found another post (not on this site) that had the same scenario. Unfortunately, the post on the internet didn't have a response. Any ideas?