My suspicion is this; there are two possibilities here. You are either missing ground or voltage to these bulbs. Considering the possibility of all of the bulbs failing at once, I would check the dimmer circuit, and the common grounds to these bulbs. The circuit gets its voltage from the taillights, and runs that voltage to the dash light circuit through a fuse. This fuse is typically labeled as such. Suggestion: If you have a test light, try checking all of the fuses in the box. A bad one will light the light on one side and not on the other. It may be necessary to turn the ignition on, and possibly the lights for troubleshooting. Let me know... Ray