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Old 18th February 2019, 15:08   #1
Yorkshire GOC
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Default Battery drain of .6 amperes

Car has been sluggish starting last few weeks - checked the battery at rest and it was giving 12.11 volts - anyway under RAC warranty and they came out and checked battery, starter motor and alternator -all fine. No OBD codes.

However he detected a battery drain of 0.6 amperes which equates to a small light being on - so does anyone have any obvious candidates for such a battery drain?
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Old 18th February 2019, 17:17   #2
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On my last car I had a 0.5A drain which turned out to be the alternator. It was charging but obvious had a fault.

Easiest way to check is get someone to help and pull a fuse at a time. That will give you a rough idea what circuit is drawing. Could also be a relay stuck on. Does the car have sat nav?
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Old 18th February 2019, 17:27   #3
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Quote:
Originally Posted by rrobson View Post
On my last car I had a 0.5A drain which turned out to be the alternator. It was charging but obvious had a fault.

Easiest way to check is get someone to help and pull a fuse at a time. That will give you a rough idea what circuit is drawing. Could also be a relay stuck on. Does the car have sat nav?
You have sort of confirmed what i suspect - despite the RAC man who came out to test the battery, under warranty, saying the alternator was fine i looked on line - there is simple test for a failing alternator diode - set the multimeter to AC voltage and then switch engine on - then apply to the battery terminals -should be no AC current at all- am getting an AC 30 v reading -so looks like a failing diode which can cause battery drain.
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Old 18th February 2019, 18:21   #4
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Be aware that our cars will draw a fairly large amount of current for about 2 minutes after being disturbed (door being open or ignition being turned on etc etc) as the BCU will be awake, it will go to sleep after approx 2 minutes and the current will drop away.


You need to put a multimeter in series with the battery on Amps (10 amp range ideally), then shut the car up, hold down the bonnet switch (or put a brick on it), set the alarm, then go away for 5 minutes or so and then come back and check the current then.


It should then be under 80mA or so really...
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Old 18th February 2019, 18:24   #5
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How long did you leave it with ignition off before checking?
Take another reading at least 30 mins after the car has had any activity and it should have gone into sleep mode by then. I left mine locked with a weight on the bonnet sensor altho that may not be needed to fool the car into thinking it was locked and alarmed ( i'm sure someone more knowledgable will be along to confirm that needed or not).
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Old 18th February 2019, 19:26   #6
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glove box?
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Old 18th February 2019, 19:29   #7
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Facelift model Smartnav box drain? I have had two and both drained the batteries quite quickly within a week or so. Disconnected and problems disappeared immediately.
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Old 18th February 2019, 19:50   #8
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Quote:
Originally Posted by neilbaker86 View Post
Be aware that our cars will draw a fairly large amount of current for about 2 minutes after being disturbed (door being open or ignition being turned on etc etc) as the BCU will be awake, it will go to sleep after approx 2 minutes and the current will drop away.


You need to put a multimeter in series with the battery on Amps (10 amp range ideally), then shut the car up, hold down the bonnet switch (or put a brick on it), set the alarm, then go away for 5 minutes or so and then come back and check the current then.


It should then be under 80mA or so really...

If my memory serves me correctly it steps down a 2nd time when you leave it longer and its sub 50mA but i couldn't swear on it.
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Last edited by Rogue; 18th February 2019 at 19:52..
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Old 22nd February 2019, 15:17   #9
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I had similar issue and changing Starter solenoid fixed the drain.
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Old 29th March 2020, 19:28   #10
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Default How to check drain....

Hi, thanks for the info within this post. Can someone tell me where to connect my multimeter to check for possible drain when alls off. Cars been fine for 5 years ( automatic diesel tourer with hi line gps unit) original battery (to me) so i presumed the battery was fubarr’d brought another but still something is draining my battery over 3-4 days ? Just need to know to to check the draw when alls off ? TIA Nev
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