Can't trace the battery drain

[daz_j]

Hi all, I’m hoping for some advice please with a parasitic battery drain problem that I’ve never been able to get to the bottom of. I’ve just got in the habit of keeping the battery disconnected as it flattens within a few days otherwise. I’ve been through some checks using advice I’ve read on the Zone. With a meter connected in series to the battery ”“ve the car is pulling around 120mA with everything off. I believe around 30mA is acceptable.

I’ve taken some readings whilst pulling fuses and disconnecting various items. These are the results so far:

All fuses in the engine bay pulled one at a time - the only ones that made any difference were 21 (drain reduced to 100mA) and 27 (drain reduced to 110mA).

All relays in the engine bay pulled one at a time ”“ no difference in drain.

Stereo disconnected - drain reduced to 110mA. Then alternator disconnected, no change. Finally alarm sounder under the bonnet disconnected ”“ dropped to around 90-100mA. It’s an after-market alarm and there’s a module under the dashboard but I haven’t done anything with this yet, there isn’t an obvious way to disconnect it.

Would welcome any suggestions on where to go from here, as long as it’s not ”˜to an auto-electrician’! Don’t want to admit defeat just yet.

Thanks, Darren (E30 1990 320 convertible).

[anothere21323i]

Have you checked the battery leads are secure? I had a battery drain in a 325i saloon which after much swearing and hair tearing out I found was because one of the battery leads in the boot was loose. Worth a try.

[Brianmoooore]

There are three or four wires connected to the + terminal of the battery, depending on the spec. of the car. The first thing to do is to determine which of these wires the drain is going down.
Keep your meter in the negative wire, and remove one of the smaller wires from the battery + clamp, then note the total current. Replace that wire, then remove another, and note the current again. Same with the third, if it's fitted.
Finally, remove all the smaller wires from the clamp, remove the clamp from the battery, then hold all the smaller wires against the battery + pole, and take a final current reading.

A loose wire on the battery may cause the battery not to charge, may cause the car not to start, but it won't cause a drain.

[daz_j]

Thanks for the quick replies - I'll follow the suggestions tomorrow and post an update.

[daz_j]

OK, I’ve followed your instructions Brian. On the + terminal there’s the main cable (wired into the clamp and going to the starter motor), plus 2 additional cables (1 to the fuse box and 1 disappears into the loom). Here are the readings:

Cable going into wiring loom disconnected: no change, drains approx 90mA.
Clamp & main cable to starter motor disconnected: no change, drains approx 90mA.
Cable going into fuse box disconnected: drain drops right down to approx 2mA.

I've pulled every fuse and relay in there previously with no success, but happy to double check?

[Brianmoooore]

Wire going into wiring loom is the main power feed for the engine loom.
Clamp and main cable go to the starter motor and alternator.
It seems that there is no problem with these.
You don't have a fourth wire, so presumably you don't have ABS.
The drain appears to be in the main feed to the fusebox, which then goes onto the ignition switch.
In the fusebox, the wire goes to fuses 21 to 28, and to pin 30 of every relay in the fusebox, except K9.
The circuit diagram also shows a couple of reverse biased diodes in the fusebox, connected between permanent, unfused live and earth, but I've never had occasion to look for these diodes, and don't know if they actually exist.

Next step is to double check that pulling out fuses 21 to 28 and all the relays does have no effect on the drain.
If no change, then unscrew the top of the fusebox (one obvious screw outside the lid, one obvious screw inside the lid, and one hidden by a relay), pull the top half up as far as the wires will allow, reconnect the battery to check that the drain is still there after disturbing the fusebox wiring, disconnect the battery again.
There is a hex headed cap screw visible from the top of the fusebox, that holds the wire from the battery to the fusebox circuit board, and to the red wire that goes on to the ignition switch.
Remove the nut from the cap screw, remove the wire that goes on to the ignition switch, refit the nut, and check the drain again, with the fuses 21-28 and the relays still out.
If the drain has now gone, reconnect the battery negative lead, and connect your meter between the red wire you disconnected inside the fusebox and the cap bolt, which should read 90mA again.

[daz_j]

OK thanks Brian, I pulled fuses 21-28 (no fuse 26) and all the relays. I did this one item at a time, noting the drain with just the one fuse/relay out, and then replacing it straight away. As seen previously only fuse 21 & 27 made a difference ”“ drain dropped to 75 & 85mA respectively.

Then in preparation for the next step I pulled all these fuses together - and the drain dropped down to 32mA.

Start: 96mA.
Fuse 21 out: 75mA
+ fuse 22 out: 75mA
+ fuse 23 out: 75mA
+ fuse 24 out: 75mA
+ fuse 25 out: 75mA
+ fuse 27 out: 65mA
+ fuse 28 out: 32mA

So a big drop with fuse 28 even though when pulled in isolation it made no difference. I carried on and removed all the relays but the drain stayed at 32mA. I didn’t progress to your next step yet as I didn’t expect a combination of fuses out to make this difference?! Is the next step (removing ignition switch wire) still valid given these results?

[Brianmoooore]

So, with all the relevant fuses and relays out, there's still a drain of 32mA? Should be zero, although I wouldn't worry about a couple of mA still leaking.
At the moment it looks like there's more than one fault, but when it's all sorted a connection between them may become apparent.
Do you have the glovebox access panels and the under dash panel off? If so, look for aftermarket additions to the plain red wire that goes across from the duct from the fusebox to the ignition switch.
There should be a red/yellow wire pushed into the accessories socket behind the glovebox. Try pulling this out and see if yo still get the big drop when fuse 28 was pulled out.
What's the audio system on this car? Just a normal radio/CD, or consisting of a head unit and separate remote amplifier?
What alarm/immobiliser is fitted, if any?
After market installations of the above two items are common causes of parasitic drain.

[daz_j]

Suffering from bruised ribs at the moment so not great for working under the dash! But I’ve had a quick look - I pulled out the red/yellow wire from the accessories socket behind the glovebox, and it did indeed give the same big drop as when fuse 28 is pulled out.

The audio system is just an old Kenwood CD/radio single unit. It doesn’t appear to be tagged on to the red ignition switch wire.

The alarm is a different story ”“ lots of wiring, difficult for me to understand. It’s a Flashpoint (Laserline) alarm/immobiliser. There’s a siren unit in the engine bay (currently unplugged) and what I take to be the control unit under the dash driver’s side. The car’s central locking is also wired in, controlled by the alarm remote control.

Neither the stereo nor the alarm has any hallmarks of a bodge installation though. In fact I have the details of the alarm’s professional installer in the car’s history. Starting to think I’m in above my head!

[Brianmoooore]

Starting to think I’m in above my head!

Not at all! We're making good progress now.

So there's 60mA flowing through the red/yellow wire plugged into the accessories socket, when everything is off?

This wire supplies power to the electric antenna in the boot, and power to the windows when the ignition is off and a door is open.
Do your window switches light up when the ignition is on?
Do they not light up when the ignition is off and both doors are closed?
Do the windows work when the ignition is off and both doors are closed. (Fuse 28 back in and the red/yellow wire plugged back in for all the above.)

[daz_j]

Not at all! We're making good progress now.

Thanks for your persistance. Just to recap current status - fuses 21-27 and all fuse box relays are still out, and everything is off. There’s 66mA drain; this drops to 32mA when either fuse 28 or the red/yellow wire or both are pulled out.

With fuse 28 and the red/yellow wire plugged back in:
The window switches don’t light up when the ignition is on, or when the ignition is off and both doors are closed.
The windows don’t work when the ignition is off and both doors are closed.

[Brianmoooore]

Do the switches light up, and the windows work when a front door is open? (Don't have the meter in circuit when you check this.)
There should be a blue relay at the LH side of the glovebox area. Pull out this relay, and check the current in the red/yellow wire.

Just had a thought! Both front doors should have been shut when you checked the current in the red/yellow wire, four posts up the thread. Was this the case?

[daz_j]

Yes I’ve had the doors closed for all the readings.

Checking with the meter in line on the red/yellow wire there’s 36mA flowing with everything off. This goes to zero when the blue relay is pulled out.

Yes the window switches do light up and the windows work when a front door is open (ignition off). Oddly the switch lights are now staying on permanently when the door is closed again. I’m pretty sure this is new ”“ certainly I’ve never noticed it before. With the meter back on the battery I now have .25A drain with these lights staying on, drops back to 66mA when the fuse is pulled and replaced killing the lights.

[Brianmoooore]

There's a plastic button fitted in the frame of each door that closes against the pin switches in the A pillars when a door is shut. Check that both of these buttons are still there.

[daz_j]

Yes they're both still there.

[Brianmoooore]

Do either of the pin switches look damaged?
Push each pin switch in by hand, with the opposite door closed, and see if the switch lights go out/relay clicks.

[bigwinn]

Daz- sorry to hijack thread but your motor looks spot on- rare colour for a cabby?

[daz_j]

...your motor looks spot on- rare colour for a cabby?

Thanks I believe it is quite an unusual colour (Malachite Green).

Brian - the pin switches both seem in good order. From off the relay clicks and the window switch lights come on when a door is opened. Manually pressing the pin switch back in doesn't turn them off again or operate the relay. This only happens when I pull fuse 28. Same with both doors.

[Brianmoooore]

Brian - the pin switches both seem in good order. From off the relay clicks and the window switch lights come on when a door is opened. Manually pressing the pin switch back in doesn't turn them off again or operate the relay. This only happens when I pull fuse 28. Same with both doors.

This is all as it should be, BUT there shouldn't be any drain through the red/yellow wire when the doors are closed and the switch lights are off.

[Brianmoooore]

So you have an aftermarket stereo at all?

All in good time! It's likely there's more than one drain.

[BenHar]

Brian - the pin switches both seem in good order. From off the relay clicks and the window switch lights come on when a door is opened. Manually pressing the pin switch back in doesn't turn them off again or operate the relay. This only happens when I pull fuse 28. Same with both doors.

This is all as it should be, BUT there shouldn't be any drain through the red/yellow wire when the doors are closed and the switch lights are off.

"Manually pressing the pin switch back in doesn't turn them off again"

That is NOT as it should be.

Ben

[daz_j]

...there shouldn't be any drain through the red/yellow wire when the doors are closed and the switch lights are off.

With doors closed and switch lights off, the red/yellow wire is unplugged and the meter is then connected in series between the male and female plugs there's 36mA flowing. Is that the correct way to test?

This is all as it should be.

Confused now - it seems at the moment the switch lights will never normally go off?

[daz_j]

Managed to get back to this today, first step being to sus out why the window switch lights were staying on when a door was opened then closed again. I was pretty sure this was new. I had been working with some fuses and relays still out from an earlier stage in this thread - after replacing them all the window switch lights now work properly again.

Fuse 21 is the one that made the difference. With this fuse pulled the lights will not turn off once they are on, and there is 36mA drain flowing in the red/yellow wire with everything off. With F21 back in place the lights work normally and there is zero drain in the red/yellow wire with everything off.

So it seems that with everything in place the red/yellow wire is not part of the original battery drain problem. But is the F21 effect I describe normal? Or is it an indication of some other wiring issue? It seems to hang together with my Dec 16 post where a combination of F21 & F28 pulled drops the battery drain to an acceptable level. Any advice appreciated please.

[Brianmoooore]

I think I can guess at the connection between fuses 21 and 28.
Undo the single screw that holds each front door pin switch in place, and pull the switch out of the hole. There should be a brown/purple and a brown/yellow wire connected to each, via separate spade connectors, connected to separate pins on each switch.
Somehow (I'm hoping it'll become obvious when the switches are out), the brown/purple and brown/yellow appear to be connected together.
The blue relay is turned on (as it should be) when a door is opened), but when the last door is shut, a current flows via fuse 21 and the interior light bulbs which is sufficient to hold the relay on, keeping the switch bulbs lit.
Note that even if I'm right on this, I don't think it will completely solve the problem.

[daz_j]

Thanks Brian, I pulled the passenger door switch but it’s a bit different to how you describe. It has 2 connections, 1 has a single brown/purple wire but the other has 2 brown/blue wires on the same spade connector. They look in good order, not touching at the switch but there’s very little slack so I can’t see much of the wiring. The driver’s side has no slack at all ”“ the connections look OK but I can’t get any wire through to look at. I’ll have to take more interior panels off to investigate further.

As I dig deeper I’m getting some weird behaviour from these F21 & F28 circuits when I try various combinations of fuses out / doors open / lights on. I need to log them down properly before reporting back.

Accurate wiring diagrams would help as the workshop manual ones I have seem to generalize a bit ”“ do you know if better ones are available online anywhere?

[Brianmoooore]

First of all, I double checked on the circuit diagram that the 'direct' interior light wire was brown/blue and the delay unit trigger wire was brown/yellow, confirmed that the relevant wire was brown/blue, but then my fingers still insisted on typing brown/yellow!!!
Brown/blue is correct, not brown/yellow, and two brown/blues on the passenger side is correct.

Both pin switches, on both doors, should have two completely different separate tabs for the connectors to push onto, with no electrical connection between them when the pin is pushed in .
Is this the case?
I'm looking for some bodging where one of the correct two tab switch has been replaced by a single tab one.

[daz_j]

No the pin switches look fine, 2 separate connections on each switch. Both connections are grounded via the switch body when the pin is out (door open). But at that point both connections are also in circuit as well ”“ is that right?

Some other effects noted today: Interior light, boot light and clock are all supposedly on the F21 circuit. With F21 OUT: the clock still works. If the interior light is activated it lights dimly and the window switch lights come on and won’t go off. Same if the boot is opened. The only way to cancel the window switch lights is to pull F28 or put F21 back in. I’m presuming none of this is normal?

[bss325i]

Wiring diagrams.

http://www.armchair.mb.ca/~dave/BMW/e30/

[e30-wheels]

Hi

Not read all the reply's but had the same problem while ago. Traced the fault to the alternator regulator.
Job can be done on the car, new regulator fitted no more flat battery

[Brianmoooore]

The possibility of alternator fault was considered in the first post of the thread, and eliminated by the fifth post.
The wiring diagrams in the link are the equivalent of what I call 'plumber's' wiring diagrams in my day job. Very disjointed and difficult to follow, and need to be 'translated' into proper diagrams before they can be followed easily. Fortunately, this has already been done here: http://www.autolib.diakom.ru/CAR/BMW/ . The main downside of these latter diagrams, is that they don't show and label connectors and splices, so the former ones still have a use.
Unfortunately, both sets of diagrams are for US spec. cars, and the loom we are interersted in at the moment doesn't exist on those, so isn't shown.

Weird effects may happen if the door pin switches are connected, the pin in the 'door open' position, and the switch body not earthed by its fixing screw to the A pillar.
Does switching both interior lights to the centre 'off' position have the same effect on the current drain as unplugging the red/yellow wire?

[e30-wheels]

Hi
Just another thought, when i had my discharge problem i read somewhere the someone with a similar problem found the fault was in the central locking module or corrosion in that area i remember reading that they were getting all sorts of weird readings not related to where the fault was found.

[daz_j]

The earth on both of the door pin switches look OK visually. I pulled out the passenger footwell panel and speaker, and had a look at the wiring to the passenger door pin switch. Again all looks OK and I tested continuity through one of the br/bl wires to earth which was fine. I'll try to do the same driver's side tomorrow.

There's only one interior light and it's been in the centre 'off' position throughout all the previous tests. With all the fuses & relays back in place and everything off there's no current down the red/yellow wire. Disconnecting it has no effect on the main battery drain.

someone with a similar problem found the fault was in the central locking module or corrosion in that area

That would be a bit of a departure from where we are but no harm in me having a look. Brian have you heard of or experienced this?