Battery drain... is it the BCU or LSM?

[Supervinnie40]

Thanks. That does help.

Currently I worked it down to
F34 = Engine management
F33 = Driver's seat belt warning, ATC controls
F32 = ABS and traction control

Unortunately, I messed up this morning when trying to measure the amps. So back to waiting again...

My biggest question is going to be: what is causing it? For example, let's say that F32 is the problem. That refers to traction control and ABS. But what to do when this is the problem? What to check? How to check what's wrong? That's going to be the next question.

[Supervinnie40]

Well, I put all the fuses back, except F34, for engine management and it gives me a reading of 0.07 amps. When F34 is put back (and I wait 2 hours), the drainage goes up to 0.38 amps.

There is only 1 thing that I don't yet understand completely. When I measure the amps I do the following:
- I pull the + lead from the battery
- I put the black pin from the multi meter on the lead
- I put the red pin on the + from the battery
- I check the display from the multi meter
- To be sure, I turn the black and red pin from the multi meter around and see if it gives me the same reading.

Normally, I get the same reading, when I switch the black and red pin from the multi meter, apart from showing a minus symbol in front of the number. But with F36 to F32 put back in, I first get a low reading, and after switching the red and black pin, I get a higher number.

For example: I just put all fuses back, apart from F34. The first time I got 0.07 amps. After switching the black en red pin from the multimeter, I get 0.38 amps.
Not sure if that is normal, or if I'm doing something wrong. If I take these 5 fuses out, I get the same reading both times.

Regardless, it seems Engine Management is throwing up the amps (I think). And the big question will now be: what's next?
What is causing engine management to make the amps go up? What can I check? Are there sensors I should check? Are there leaks I should check? I don't know to be honest...

[SD1too]

Originally Posted by Supervinnie40

Currently I worked it down to
F34 = Engine management
F33 = Driver's seat belt warning, ATC controls
F32 = ABS and traction control

More specifically Vinnie:

F32 = ABS ECU (Traction Control not applicable to the 1.8)
F33 = ATC ECU, driver's seat belt buckle switch (white/orange wire). These are supplied via header connector C0723.
F34 = Fuel pump relay coil, ECM

F32 & F33 are only live when the key is in the "ignition on" position.

Your meter probe connections are correct. DC current flows from the battery positive terminal, through your meter from red (positive) to black (negative) then into the car's red battery clamp. Don't reverse your meter leads, you risk causing damage.

Simon

[SD1too]

Originally Posted by Supervinnie40

What is causing engine management to make the amps go up? What can I check?

I'd start with the plenum rainwater drains.

Simon

[Supervinnie40]

Originally Posted by SD1too

More specifically Vinnie:

F32 = ABS ECU (Traction Control not applicable to the 1.8)
F33 = ATC ECU, driver's seat belt buckle switch (white/orange wire). These are supplied via header connector C0723.
F34 = Fuel pump relay coil, ECM

F32 & F33 are only live when the key is in the "ignition on" position.

Your meter probe connections are correct. DC current flows from the battery positive terminal, through your meter from red (positive) to black (negative) then into the car's red battery clamp. Don't reverse your meter leads, you risk causing damage.

Simon

Thanks for the confirmation. I'll continue testing with not switching the pins around.

Originally Posted by SD1too

I'd start with the plenum rainwater drains.

Simon

I check these weekly, but never hurts to check once again. They are bone dry and all plenums are clear. I can see the pavement under the car. Ecu looks a bit dusty at most, but pretty clean and dry. No signs of moisture or waterlines on the cabin filter either.


Unfortunately, the car has made me scratch my head once again. Really confused now!

I realized I never tried what happens when I simply leave the multimeter attached. Not disconnect it all the time. So I got a few clamps and attached the multimeter as above, and left it in place.

First sign (with the 5 fuses mentioned above removed, I saw that the current goes up when the doors have been opened. When I close the doors, the current drops after roughly 1 minute down to 0.06 amp.

I then saw I didn't connect the alternator (took it off last night). So I put that back, and openen a few doors. Amp went up at first, but dropped after a minute to 0.07 amp.

Finally, I put all 5 fuses back and connected everything in the car as normal. At first the amp went up (just opened a door), but eventually it dropped again down to 0.08 and stayed there.

So, with the multimeter connected (and not pulling it loose all the time), the amps go down as can be expected. (0.08 is reasonable I think?)
But if I disconnect the leads, and reconnect them, the amps go up to 0.3 amps, without touching the doors.

I'm starting to loose the plot haha.

[SD1too]

These are the maximum expected current drain values from MGR Technical Tip no. TT0036:

Engine running: 10.0 - 11.5 amps
Up to 18 minutes after ignition switched off: 1 - 2 amps
More than 18 minutes after ignition switched off: 0.030 - 0.045 amps (30 - 45mA)

Does your meter have a 200mA range which you could use for a more accurate reading once the current has reduced to a safe level?

Simon

[Supervinnie40]

The battery is on the charger again, but I will try the 200ma setting when it's done.

My biggest confusion right now is that I saw 0.03 amps on the multimeter. That is 10x lower then what I've been seeing so far.
I started a week ago with 0.45 amps, because it was draining the battery. I have been pulling fuses, plugs, connectors and other stuff. Never found anything decent.
I finally thought I found the problem when I pulled the BCU, but after more testing I'm starting to doubt that as well. Today I got 0.03 with the multimeter staying in place. That seems acceptable and shouldn't drain the battery at all.

So, if the above is done correctly, I honestly don't know why my battery keeps draining. This is the second battery in 8 months. It's getting a bit expensive this way.

[Supervinnie40]

This is the amps after connecting everything and waiting for 10 minutes. Battery has just been charged.
I'll check again in about 2 hours to see if it has changed.

In case it matters: the car is unlocked with a clamp on the bonnet switch. I closed the boot as last, and waited 10 minutes to make the photo.

It's a tad high, but already lower then in the past.

[Supervinnie40]

After 2 hours I checked again. I left the multimeter untouched after the photo above.
The result is that is constantly fluctuates between 00.7 and 00.1. It takes about 2 seconds to drop to 00.1 and to climb back up to 00.7. Sometimes it goes to 00.3 and then back down again to 00.1. I tried moving the cables or the pins around, to check if it was a bad connection, but moving it around made no differecen. Only when I disconnected the multimeter, and connected it again it would go up to 04.3 and eventually (after a few minutes) drop to 00.7 again.

[Gluey]

Hi, do you have a Satnav CD player. My 2005 Tourer suffered the same problem and I found a reply advising that the CD drive did not close down. I removed it and have had no battery loss since.