i have the same isue on my 89 300ce,i turned my lights on the othernight,there was no interior lights,i had just reset the trip odometer,then i wiggled the dimmer switch,andthe lights came on,i agree with the others the contacts are dirty,however i dont know if it just pulls out to clean,or if you need to remove the dash,goodluck. i believe on my car it is fuse number 9 underhood on drivers side next to brake power booster.