Eventually, the switch illumination or 'on' button bulbs are going to burn out. New from Subaru, the bulbs are about $8. Each. Thankfully, they are not hard to replace with easily available bulbs from Radio Shack for $2 pair. These bulbs have worked in just about every Subaru I've owned that used mini bulbs in the switches, from my 1992 SVX to my 2003 TS Wagon. Any questions or comments, please feel free to email me.
This is a fairly easy process once the dash switches are out. This is done in a variety of ways, many covered on this site, and this page assumes you have the switched out of the car already. Here we have a switch ready to go, and the replacement mini bulbs from Radio Shack, part 7219, 2 to a package and $2 a pack. The bulbs are underneath the little round blue and gray fittings- they come in a variety of colors, and are often also black or brown.
A closeup of the bulb bases- these come out by putting a flathead screwdriver into the + and turning about 1/16th of a turn counterclockwise. You should be able to either shake the bulb base free, or use the screwdriver to pop them out.
The bulb and base after being removed from the switch. Depending on what the switch came out of, the bulbs may have small colored covers on them. You will need to carefully remove them by pushing from the base of the bulb towards the top, and save them for later.
Using a screwdriver or other small implement, pull the wires from around the posts towards the back of the bulb base, straightening them out. You can then pull the old bulb out of the base.
Push one of your new bulbs through the base, one wire through each of the little holes in the base.
Next, wrap the wire through the slots towards the front, over the post, and back around to the back side of the bulb base.
At this point, I put the bulb and base back into the switch, because it will hold the bulb in place while you cut the long ends of the wires. Push it into place and give it a turn clockwise to lock it back in place.
Snip the long ends of the wires off, and push them flat into the small grooves, and you are done.
Standard Disclaimer: Modification of your car involves risks and may void your warranty. I can not be held responsible for the modifications you consciously decide to undertake nor for the results of doing so.