Have just been replacing the tail light bulbs on my car and have noticed that the bulbs are working differently either side. the bulbs 21/4 watt types. the have two elements and two contacts, one for each element. The tail light bulb on the left hand set of rear lights, both elements light up when you turn the lights on and is very bright. But on the right set of rear lights, only one element lights up and is very dull. As an electrician by trade I have inspected the contacts for both lights and they are not damaged or corroded. I looks like the contact on the right tail light as been manufactured to only touch one element which does not seem right. Does anyone know if both elements are to work????