"I wish I could tell you how to do it without breaking it. Every one I've ever seen is already broken. It may very well be built that way to provide tamper evidence." That's exactly right Art. Don't fret about the plastic ring--insert the blade of a straight screw driver into the loops on the outer ring and give a twist to break it. Once the outer ring slides back you can unscrew the cable cap. If you haven't already popped the panel loose from the dash--here's how--put a largeish pry bar/screwdriver between the upper edge of the instrument panel and the lower part of the "hood". The panel is held in place with some powerful spring clips at the top. Use the pry bar to gently push the panel downward while you use your other hand to push the panel out from behind at the top. While you have it out drill or punch a few holes in the tinted plastic strip at the top of the panel to bring more green light onto the instruments---and check the string of (3, I think) panel illumination bulbs under the "hood". -- Dave