E34 Battery Drain

I have an 1995 E34 518i SE and it has been draining the battery overnight for the last 2 nights. I had the RAC out yesterday and they found that there
was a 1.5 amp current draw causing this. I also noticed yetserday that there appears to be a buzzing noise coming from behind the centre air vents. When fuse 20 is removed both the current draw and the buzzing noise stop. If the fuse is re-inserted the buzzing noise remains stopped. I have removed the relays in the fuse box one by one to see if one of them is causing the problem, but none stop the noise. Could someone please advise if there are any other relays that may be at fault and if so where they are located or can someone suggest what to check next.
Thanks in advance, Hamid
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There are motors which shut the fresh air vents when you switch off. And if you measure the current drain while this is happening, you'll not get a true reading. You need to check it after they have stopped. If there's still a noise after a few minutes, this needs checking.
1.5 amps is a strange figure.
A relatively common cause of a good battery draining overnight is a failed diode in the alternator. But this takes more like 5 amps.
I'd expect a battery in good condition to survive an overnight discharge of 1.5 amps.
--
*Some people are only alive because it is illegal to kill.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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London SW

Thanks for the response Dave. When the RAC guy checked the current drain, the car had been switched off for quite a while (30 mins). If I put my ear against the dash next to the vents, I can hear the buzzing noise quite clearly. I'm not so sure that the battery is in good condition as it is the original one. One strange thing that happened yesterday very briefly was that the odometer started flashing and at the same time the cd in the stereo started jumping.
Regards, Hamidf
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Hamid Saeed wrote:

It looks like fuse 20 goes to all sort of climate control stuff. Your going to need to make it happen again and then tear into the dash to find out what motor is running continuously after shutdown.
-- -Fred W
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Thanks for your help Fred.
Regards, Hamid
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