Ed is correct.
I just replaced the whole fixture in my head, since it wasn't the bulb that was bad, but something in the electronics that makes it possible for a florescent bulb to operate on 12 volts. I discovered that the fixture was wet, which may be a reason it failed. My wife used to keep the port open rain or shine to help re-cycle the air. The water had to go somewhere; right into the fixture.We will now close the port in rainy weather. By the way, I found the prices of florescent fixtures to be far lower than the "marine" outlets when I purchased out of a J.C. Whitney catalog under the RV section.Ken Palmer, S/V Liberty