Just burnt out, different brands. The battery is o.k. I think.
Very strange! I only see two possible causes: too much
vibrationys or unstable voltage. Or maybe the bulbs overheats in
these tight lens headlights.
I'd start by checking the voltage across the battery terminals at
fairly high (autobahn/motorway) speeds. There are cheap
digital voltmeters over here (UK). Just run a lead through one
of the bulkhead grommets. Round about 14.4V is an upper
figure but depends on battery mfrs. recommendations.
14.5V or over needs investigating. Charging systems carry
heavy currents so conections and lugs need to be clean.
Best to test at speed during daylight, headlamp load will pull
the voltage down, so if it's ok in daylight it should be ok at
night. What might be happening is you are overcharging,
raising the battery volts, then you put the lights on across
this higher voltage, and phut.
Just a thought... do you start the car with the lights switched on? It seems
that sometimes, just when the engine is about to run while starting it, a
higher (peak)tension in the boardcircuit can occur (forgive my bad
tech.english). This seems to shorten the life of your headlamps
considerably. At least, that is what i found with our own MK II. So i turn
my lights on after startingprocedure. Overheating is not an option in my
opinion. The headlamps of my MK II have lifespan for about two years, and
that's not bad i think.
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