parasitic amperage drain ?

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SGP
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Post Wed May 27, 2015 8:14 pm

Hi, I've traced a .271amp drain on the battery (all systems off) back to the blue plug on the instrument cluster. When it's disconnected the draw falls to .004a It's the Circuit fused by no. 21 (7.5a). No stereo system or alarm currently fitted, and everything seems to work properly inc. instruments,check panel, obc and all the bulbs on the circuit.
What should I do next ?
Any advice greatly appreciated. (89 320i se)
If it ain't broke..
Fix it till it is :)
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Brianmoooore
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Post Wed May 27, 2015 10:26 pm

Are you sure it drops to 0.004A (4mA) and not 0.04A (40mA). 4mA is extremely low for the static drain.
Conversely, 271mA is extremely high.
If you're certain that the majority of this is disappearing through pin 2 of the blue instrument cluster plug, then I'd check out the SI board batteries.
Do the SI LEDs work as they should?
SGP
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Post Thu May 28, 2015 11:14 am

Thanks Brian, I must be reading the meter wrong. I had a look at the si board, no leaks from batteries, three leds are lit, and the inspection light is on. the board looks new, the batteries are at 3v, and don't know how to isolate pin 2. On close inspection there seems to be a repair to one of the tracks on the back of the board.
Image
Image
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SGP
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Post Thu May 28, 2015 8:00 pm

It's enough to drain a fully charged battery in a couple of days. I'll try another binnacle..
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Fix it till it is :)
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Brianmoooore
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Post Thu May 28, 2015 8:35 pm

That'a lithium battery board, which doesn't have a charging circuit for the batteries, so that's one theory gone west!
These boards do have a number of odd faults that they can develop though, and it looks like you may have found a new one, so trying a new cluster would be the right move, if you have one, and if that cures the problem, it would be interesting to swap the SI boards between the two clusters, and see if the fault follows the board or the resr of the cluster.
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Post Thu May 28, 2015 10:13 pm

I've changed the si board for another spare (also lithium batteries ). The draw has fallen to 0.07 on the 10ma setting. 70ma ? This si board is not illuminating the 2nd green led from left.
Is this another typical lithium powered fault ? (system was reset)Image[/URL]
If it ain't broke..
Fix it till it is :)