Mini Cooper S 2003: Battery drain

[Cooper S Jon]

now you've gone to a digital meter,read the charging voltage again with the engine @ idle with no load..

[jmb]

Hello,

Firstly, thank you for your suggestions so far. I hope this is creating a useful thread on DIY battery drain diagnosis.

I had read again and it's now 15v with the engine running and no load. So I reckon it's charging. However I have new information, please see attached photo.

I suspect the fat cable that's helpfully holding down the masking tape (which is in turn, holding the positive from the meter on the battery), is the wire to the alternator. I've unbolted the lead to which the meter negative is connected, and I can see that is connected to a fuse, so I assume it's the wire to the fuse boxes.

The meter read 500mA when connected, 200mA after about a minute but only for a few seconds as it dropped to 120mA. I've left it for half an hour and it remains at 120mA. However, during one of the tests, I noticed 10mA but foolishly walked off for a tea and came back to find 120mA. I can't explain this "blip".

I've also put the meter near the car window with all the doors/boot shut, but the 120mA reading remains.

I've also connected the meter between the battery (positive) and the wire that I assume goes to the alternator, and nothing is measured.

Given I've pulled all the fuses and the drain remains, I guess this leaves two possible explanations:

1. There is water or something on the back of a fuse box.
2. The immobiliser is drawing power.

(I welcome all other explanations/theories!)

Does anyone have a page from the Haynes manual that shows how to unwire the power to the immobiliser, and also another showing the removal of the fuse boxes? I assume that a single wire must plug into the back of each fuse box so eliminating faulty boxes (perhaps damp that got into them) would be a helpful step.


John

[Restyle]

You're getting slightly confused with your meter readings - On the 10Amp meter scale shown in photo 0.12 = 120mA or 0.12Amps & not 0.12mA.
{1mA milliamp = 1 thousanth of an Amp}
Which is still a low figure, but around twice as high as it should be.

However, before you go & start removing any fuseboxs etc, Ive found a thread that might have a couple of answers for you >> http://www.mini2.com/forum/first-gen...i-glos-uk.html

{Basically - Removing the battery for a couple of hours, & if possible charging it fully with a seperate charger while its removed, might cause the computers to reset & remove the parasitic drain down to normal levels}

Ive also checked through the Haynes manuals for any relevant info - but they're pretty useless !!

Happy Christmas

[jmb]

Hello

I've been disconnecting the battery between diagnosis attempts, so it has been disconnected for days. I'll try charging the battery but if I've removed all the fuses, which I assume includes the computers, I would expect the drain to be related to something else.

Do the Haynes manually really not provide any useful feedback on getting to the back of the fuse box? Or how the immobiliser works/is wired?


John

[Restyle]

Quote: Originally Posted by jmb (original)

......Do the Haynes manually really not provide any useful feedback on getting to the back of the fuse box? Or how the immobiliser works/is wired?

Haynes manuals seem to have become lacking in any crucial info probably from the 80's onwards - where they used to describe how to change regulator units in alternators or swap the brushes in starter motors.
Nowadays its just 'get an exchange unit ' or 'consult the manufacturer' !!
.... & they're printed on the cheapest possible paper.
{IMHO}

Anyways, see for yourself the relevant pages below

More thoughts about Normal Parasitic Drain Current
The alarm unit when active is sending out & detecting a stream of continuous ultrasonic pulse's - and flashing the stalk indicator.
A radio receiver is continuously scanning for an 'Unlock' signal from the key remote.
Backup power is being delivered to the computers & clock.

Are you sure a 120mA drain isnt the norm for your spec car? - what figure does the dealer give?

Also, Am I right in thinking your battery drain photo was done with the boot open ?- all tests should ideally be done with the meter visible through the rear window of a closed & locked boot so as not to interfere with the alarm systems etc
{Im guessing you've probably taken this into consideration already - but might be useful info for anyone else doing these tests}

[jmb]

BMW tell me 120mA isn't normal, it should be <20mA. I've pulled all the fuses, so it only leaves the immobiliser. I'm not sure the alarm is working when the fuses are pulled and the red flashing light certainly stops, particularly when I haven't locked/armed the car (key stops working).

I've shut all the doors and left the meter in the window. I left it for 30 minutes without fuses and the alternator, but it still drew 120mA.

[jmb]

Hello,

I've got an update on the problem.

Please see attached picture. This is the engine compartment fuse box with all fuses and relays removed. In the top left (which is middle left given the forum as rotated the picture!), the cable that goes back to the battery can be seen bolted onto the box. With all fuses removed, the drain remains at ~120mA. When the battery lead is disconnected, the meter drops to zero. However, nothing else works, ie I can't turn on the radio.

Is the internal fuse box fed via this fuse box?


J

[jmb]

Any thoughts before I give in?

[BornToRunInMD]

JMB, don't give in! I have a 2005 JCW Convertible with exactly this problem - it is making me crazy. I tried to trace out the leak by pulling my fuses last October (when the weather here was more accomodating) only to find out that my VOM was shot and needed to be replaced. In the meantime I've gone through one new battery and countless jump starts from the trusty Honda Odyssey. I'm going to try to trace out the bad circuit, including disconnecting the alternator, this weekend. Will let you know if I make any progress....

[mikemic]

My first post. Wanted to pass on some info on the battery drain problem in my 2003 Cooper S, now fixed I believe.

My battery drain appears to have been caused by the Harmon Kardon amplifier. The battery would completely discharge overnight. Removing the amp (right rear of car, easy removal) seemed to completely solve the problem (a week and a half since I did that and no battery drain). I believe the amp has some sort of small short. I found a few posts on BMW "M3 cutters" forum where someone else had a battery drain problem caused by a faulty Harman Kardon amp. My amp works almost perfectly, but one other sign of an amp problem was occasional no sound when stereo was turned on - only solved by turning ignition on and off.

Unfortunately neither Harman nor BMW will fix amps. Replacement is $1600 Cdn from BMW. And installation of aftermarket is difficult. BUT, there is one cheap solution to this problem that I had done today for $100. The amp has one or two power supply wires that are constantly hot. There is another wire that sends a signal to tell it to turn it on. The solution was to install an electric trigger swith (relay) into the two power supply wires just before the amp. So the amp only receives power when the ignition is on, as opposed to getting power all the time. So when car is off there will be no possible drain. Was a $15 part and 1 hour of labour. And just a few wires and switch in there around the amp. Done by a stereo shop. We'll see if it works. Pretty sure it will. Sorry I can't give more details on the install, was done by a shop. But any stereo shop should be able to do this.

So if you have an unknown battery drain, and a HK system, check the amp.

[mikemic]

Sorry, I should have also mentioned that simple removal of the two (5A and 15A) stereo system fuses under the dash fixed the battery drain, and was what suggested the problem was something with the stereo system. Then when I put the fuses back in but removed the amp the battery drain stayed away, so figured the problem was specificall with the amp part of the system.

[mikemic]

The installed cut off switch to the amp's power supply appears to have fixed the problem.

Also, my previous "follow up" comment may not have been 100% accurate. I'm not sure if simple fuse removal stopped the amp battery drain. I may have also unhooked the amp when I pulled the fuses.

So final word of advice is simply unplug HK amp and see if that solves things for a week. Good luck.

[ciscoprog]

Does your radio have a fuse? I'm sorry but I am not technically advanced when it comes to this but I did have a 2002 VW Jetta VR6 that had a small battery drain for years until finally it got pretty bad. Several returns to the dealer and they found the radio was draining it very slowly even while turned off. This car had lots of "amenities" that were electrical. $400 later, they found the problem. Good luck.

[planman]

Just thought I would add my five pence worth for relative interests sake.
I also own a Mini Cooper S 2002 from new, the first year had flat battery problems which was down to corrosion to the lead to the steering power pump which earthed the lead to the body. New pump and battery under warranty sorted the problem.