Sorry, should have said, the actual PROBLEM prong in the connector is the EARTH one, you can find it because it's the one common to all the bulbs in the cluster/bulb holder - ie there is a metal track that is common and that's the earth or negative, the return route to the battery for the electrons that have gone through your bulb filament to make it burn brightly! Another guy said there is a back-feed, this is correct, it's occurring because the earth route is not good enough, TWIST THE EARTH PRONG and refit - NO COST, just fine-nosed pliers (ie long pointy ones). DONE!