Rear tail light

[andylep]

Need help with following issue, when I open the car all the tail lights come on as they should, as soon as I start up the engine the n/s outer tail lamp goes out, all bulbs are good and earth seems OK, hopefully this is something simple, The car is a 2009 c220cdi clk

 

[OneForTheRoad]

For a few quid , buy some new bulbs and try them in there.

Or swap them from the o/s and see if the fault moves with the bulb.

 

[Trickythemerc]

Are you getting a bulb failure warning ? Older or cheap chinese bulbs can cause all sorts of problems, even though the bulb appears good it could be end of life. Any sign of darkening of the glass is a sign of impending failure, over time the resistance of bulbs changes and this will spook the bulb failure warning system.

 

[markjay]

For a few quid , buy some new bulbs and try them in there.

Or swap them from the o/s and see if the fault moves with the bulb.

As above.

When you start the engine, the voltage goes up from 12v (battery) to 14v (alternator). The bulb might not be happy with the higher voltage, for some reason.