Help! my near side rear tail light is faulty, I've changed the bulb but it still won't light. Unless.. I switch side lights on first and then insert bulb, however when the lights are switched off it won't come back on again until it is removed and put back in! The brake part of the light works ok as does the indicator, lots of head scratching but I see no logic to the problem. Any ideas please before a trip to the auto electrician has to be booked, the car's an '01 plate 156, thanks .