Well the good news is that it should be an easy fix or at least prognosis. Is the power jack making any noise at all? Any type of hum or grind or anything?
Fuses, especially small ones, can wear out over time. That's what it sounds like here. Probably the jack and the control panel are wired to the same fuse. I assume you've checked that?
If you have and that's not the culprit, trace the wiring from the jack to the interior and see where it's connected in the fuse panel. Check the leads as they go into the fuse panel and make sure they're connected still with no marring (burning discoloration) on the screw that holds them in place. If it all looks good and the fuse checks out, remove the leads from the fuse panel and use alligator clips to your battery (assuming the fuse panel and the battery are near each other) to see if it works. If it doesn't, and there are no inline fuses that have blown, you've got a bad power jack.
I still say fuse though.