Micra headlight!!

[d10 ldo]

Hi, i've got a problem with the left hand headlight? It goes out from time to time, checked and replaced the bulbs, the same! Had the wire from the switch to the bulb holder, the same! Changed the bulb holder and yes its still the same? When i check the wires for current, with the bulb out, i get one wire with current (depending on wheather its headlight or main beam), but with the bulb in all three wires have current? I've thought maybe the earth or even a relay? Can anyone help please?

[dragstar]

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