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1999 C2 996 - Humming noise from engine bay when Alarmed & Horn al

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Hi all


I'm looking into a battery drain issue on my 1999 996 UK Cabriolet Porsche.

Just a question for other 996 owners (early 996 owners prior to 2002):


Question 1:

When my 996 is locked or unlocked, I always get a Very quiet high pitched humming noise coming from the engine bay - If I put my ear to the Spoiler vents I can hear it. And If I open the engine lid, i can of course hear it better. I cant tell where its coming from, its very quiet but is there All the time, locked or unlocked.


Is this normal and do other 1999/2000 996 owners have this noise all the time?


Question 2:

When my 996 is locked or unlocked, I always get a very quiet "clicking" sound coming from the Alarm Horn (not the Siren). I can hear this noise with the bonnet closed and my ear next to the wiper arm/plastic water tray area (just above the horn really). This noise is constant and there if the cars unlocked or locked.


Just wonder if other 996 owners have this noise from the horn (its very quiet but you can hear it clearly with your ear close to the Horn)?


Just really trying to check these two area so I can discount them or see them as two faults. I dont know any 996 owners, so hopefully someone on this forum can check theirs!


Many thanks,


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After the engine has cooled overnight, lift the engine lid and put you hand on the alternator.  If it is warm then the diodes are going bad in the alternator, which can also cause your battery drain.  Not sure about the clicking noise, but could it be related to the battery drain problem and low voltage?

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  • 2 weeks later...




Just to confirm that the alternator was faulty and had bad diode/s, this was indeed causing the Hum noise and the battery to be drained after 4-5 days approx (350ma of excessive drain - so 400ma approx in total drain when the car was locked and 1 hour surpassed).


I got the alternator repaired under waranty!




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