Extreme Battery drain on JCW

[RachyS]

Excuse me here, I'm using the Mrs account in search of a little help from the Mini experts!

Her 05 JCW has been having issues for the last couple of months where by the battery is dying in just a few days. She's asked me to sort it out for her... I've been putting it on trickle charge over night every few days as I havn't had a chance to look at it but last week I stuck a new Bosch battery on it thinking this was the problem after the recent cold spell. Well guess what... 4 days later and it's flat again! So there is definitely a drain on it somewhere.

I've put a meter across the battery with and wothout the engine running and it's definitely charging so the alternator is fine.

I've checked the current draw on the battery with the car locked and everything off. It's 2.45 amps for the first 30 seconds or so, until the interior lights die out etc. After 30 secs it drops to ~0.57Amps.

From the searching I've done so far, I have found this thread which suggests current draw should be around 16mA. Well this is considerably higher!

I've gone through the fuseboxes both in passenger footwell and engine compartment. Pulled every fuse whilst monitering current draw. There were 2 fuses I found that made a difference when removed:
One was F21 in the passenger footwell box. A 10amp fuse for the Rev counter clock in the centre of the dash. The current draw dropped from 0.55 to 0.35. A drop of 200mA.
The second was F27, again in the passenger footwell box. This is the 15amp for the stereo I believe. It dropped to 0.42 with this one pulled. With both the above removed it was down to 0.18.... 180mA still suggests a problem to me

The car does have the HK sound upgrade with Amp in the boot and a 6 disc changer. I have a feeling one of these are to blame but I havn't tried unplugging these yet. That's tomorrow nights job.

My worry is why are the dash clocks drawing 200mA ??

Anyone give me any pointers on where to go from here/what to test next?

Thanks

[RachyS]

I stripped the back end of the car down at the weekend, removed the 6 disc changer which made no difference to current draw. I then removed the Amp which dropped the draw by 0.15A, the same as when I removed fuse 27, so this confirms the HK Amp is responsible for 0.15A of the total 0.57A current draw, but why is the rev counter circuit drawing 0.25A and where is the other 0.18A draw coming from??

Any ideas??

Thanks

[The Nun]

Alarm system?

[RachyS]

Would the alarm system be drawing 180mA though?


There is a fuse for the ultrasonics which if I pull, sets the alarm off, but I doubt that's for the brain of the alarm.

I don't even know how the alarms work on these cars. Are they built into the ECU or is it a seperate module?

[mab01uk]

This is the PDF file for the official alarm retrofit kit which may help:
http://www.motoringfile.com/howto/Alarm.PDF

[RachyS]

Is there a 3rd fuse box in a MCS that I have missed?

[nine11]

You say

Quote:

I've put a meter across the battery with and wothout the engine running and it's definitely charging so the alternator is fine.

How do u test the alternator without running the engine?

[RachyS]

Quote: Originally Posted by nine11 (original)

You say

How do u test the alternator without running the engine?

The Alternator only runs with the engine on. When the alternator is running, the battery will return a higher voltage of around 13.5-14v through the multi-metre. Without the engine running you will only see around 12v. Therefore if there is a significant difference between the battery voltage with the engine on and the engine off then you know the increase is due to the alternator charging the battery. If however the battery voltage remains the same, or starts to fall with the engine running, you know that the alternator is not charging the battery.

[RachyS]

Update!

Today I removed all fuses simultaneously. I hadn't previously removed any of the big (50A) fuses in the box under the bonnet. It turns out on removed of FL12, the current draw fell completely to Zero.
Apparently FL12 is the Headlight Circuit.. So:

I have a draw if around 180mA from the Head light circuit.
A draw of 200mA from the Auxiliary instrument cluster (Rev counter)
A draw of 150mA from the stereo circuit.

That's 3 separate issues as far as I can make out.... Now where the hell do I start! Any advice welcome

[MrLoz]

I thought modern cars were supposed to go into hibernation in terms of battery drain after a set time of being idle. Maybe the system responsible for this is faulty and therefore allowing current drain/ not shutting down circuits. There is a post on here about the body control unit and the CANBUS and how it all works. Worth a read to understand how all the separate systems work and communicate.

I would have thought only the clock and alarm system continue to drain after locking the car and leaving to stand. The current to keep memory alive should be minute. The alarm system should cause such little drain that the car can be left for weeks without bring run. I have left our cooper S convertible three weeks in cold weather and started without any sluggishness.





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