My tail light keeps going off, other bulbs ok. I can get the bulb back on if I take it out and put it back in but sometime by the time I've screwed the cluster back in it's off again when I test it! I've tried a new bulb but no luck. Any ideas? What's the part called which all the bulbs plug in to called? I've got a multimeter but obviously I can put one terminal on where the bulb touches, but where do I put the other one? Thanks for any help I appreciate it.