Electrical Drain FUSE 21

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Kryptonite
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Mon Mar 06, 2017 9:25 am

Hi.

I've isolated it to that circuit. Slow drain but flattens the battery after about 4 days.

I've noticed that my fog lamps lights under the taco/speedo are oddly very faintly illuminated. My Speedo doesn't work with or without Fuse 21 and I should also add that my left Foglamp is not fitted whilst I wait for a replacement.

Any ideas?
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Brianmoooore
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Mon Mar 06, 2017 9:59 am

Boot light staying on (not Touring) is a favourite for drain through fuse 21.
Can't connect fuse 21 to the foglights in any way at all. No cross connection between the circuits at any point.
Need to know what the actual current is through fuse 21, in mA, when the car is off. A few 10's of mA is normal.
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Kryptonite
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Mon Mar 06, 2017 10:33 am

So I measured it again.

71mA without Fuse 21 - 144 mA with Fuse 21 fitted.

I should also note, when the boot is open, the boot lamp is very very dim so as to be practically useless - but obviously the bulb is ok.
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Kryptonite
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Tue Mar 07, 2017 9:41 am

Bump.
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Brianmoooore
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Tue Mar 07, 2017 10:04 am

Sounds like you may have multiple issues here!!
73mA through fuse 21 is very high, but not ridiculously so. Where/how are you measuring the total (144mA) drain, and any pointers as to where the other 71mA is going?
The red/green wire from fuse 21 goes to a junction inside the loom, low down towards the sill on the passenger side, where all the wires to the various functions served by fuse 21, radiate from. There have been cases of this junction becoming corroded as a result of damp from the footwell, which could be relevant to your dim boot light, but it's difficult to see why problems here would increase quiescent consumption.
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Kryptonite
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Tue Mar 07, 2017 10:31 am

Thanks Brian.

I'm placing my meter between the battery negative terminal and battery ground clamp.

Where the 'other' 71mA is going - not sure I understood your point there?

Could it be radio related?
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Brianmoooore
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Tue Mar 07, 2017 9:07 pm

That's the correct place to put the meter.
The radio (if fitted as BMW intended) draws power through fuse 21, and should still draw a small amount with the car shut off, but nowhere near 73mA. Part of the problem could be radio related, but there's no evidence one way or the other yet.
The 71mA I'm referring to is the rest of the drain. You say it's 144mA with fuse 21 in place, dropping to 71mA with it removed. The only other things that should draw current with the car off, that don't get their power through fuse 21, are the central locking system, through fuse 27, and the immobiliser/alarm/remote locking/unlocking, through fuse 28, if it's connected as BMW intended. Again, these should draw nothing like 71mA.
Remove fuse 21, and try to find where the 71mA is going. First try pulling out fuses 27 and 28, and if that doesn't reduce consumption to a few micro amps, remove the small wires (either two or three, depending on the car's spec.) from the battery + terminal, just leaving the clamp itself and its thick black wire.
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Kryptonite
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Wed Mar 08, 2017 7:55 am

Thanks Brian - will report back!
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Kryptonite
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Wed Mar 08, 2017 4:24 pm

Ok.

I found the and removed the unrelated drain. With Fuse 21 removed it now reads 4.1mA. With Fuse 21 attached it reads 136mA.

Removing Fuse 27 and 28 makes no difference.

In the image below, removing the BIGGER of the clamps on the right make no difference. Removing the SMALLER ring terminal on the left drops voltage to 0.17mA WITH Fuse 21 fitted.


Image


Some other info that may help. The Speedometer does not work with or without Fuse 21. I think it may be to do with the diff sensor as I replaced the diff not long ago and noted the plug was not in good condition - could be shorting?

Also, the radio fitted has Bluetooth phone support and a Microphone fitted in the headlining. The Mic stopped working about the same time as the drain started though I can't be sure it was a long time ago.

I guess the next step is to disconnect the radio and WITH Fuse 21 attached and see if that current draw drops?

One other thing - the clocks (speedo / taco etc) have very poor illumination.
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Carmo13
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Thu Mar 09, 2017 12:36 am

Do you know that rotating the headlight stalk adjusts the clocks illumination?
It may just be that its turned right down.
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Kryptonite
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Thu Mar 09, 2017 7:42 am

Carmo13 wrote:Do you know that rotating the headlight stalk adjusts the clocks illumination?
It may just be that its turned right down.
No buddy it's dim on the highest setting.
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Carmo13
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Thu Mar 09, 2017 9:15 am

Ok mate, just a thought.
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Kryptonite
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Thu Mar 09, 2017 9:24 pm

Anyone had this issue? Am conscious that 'B-Mo' is in high demand time-wise!
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Kryptonite
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Mon Mar 13, 2017 10:17 am

Have removed radio with no drop in current draw so it's not that...

Anyone help with the image I posted?
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Mon Mar 13, 2017 12:54 pm

Are the interior courtesy lights working correctly?
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Kryptonite
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Mon Mar 13, 2017 1:28 pm

DanThe wrote:Are the interior courtesy lights working correctly?
Yes.
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Contours
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Mon Mar 13, 2017 2:19 pm

Have you considered that you may have a weak battery on the way out or some power source connected directly to the battery that does not go through the fuse box at all.
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Kryptonite
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Mon Mar 13, 2017 2:26 pm

No.

Brand new battery and any aftermarket stuff has long since been removed.

The drain is isolated to the smaller of the 2 additional ring terminals at the main + terminal.

I don't know what it does / supplies.
DanThe
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Mon Mar 13, 2017 6:49 pm

Its the supply to the fusebox
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Kryptonite
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Mon Mar 13, 2017 7:47 pm

DanThe wrote:Its the supply to the fusebox
So that's narrowed it down lol.

Fuse 21 controls radio and instrument binnacle - anything else?
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Kryptonite
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Mon Mar 13, 2017 9:40 pm

Not radio, not clocks, not lighting. Glovebox / torch charging socket maybe?

Will try that tomorrow but after that am stumped.
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Kryptonite
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Tue Mar 14, 2017 11:09 am

CORRECTION - It's the radio. :mad:

With radio removed it's 13.6mA and with radio it's 136mA - you can see where I got confused.

Not sure if 136mA draw is normal for a radio - am trying to find the 'resting' current draw for my model (Becker Cascade). It does have a pair of passive crossovers wired in between it and the speakers which are components front and rear but as I said, they are passive so don;t think they would affect it.

Removed the iPod and Mic inputs, GPS and antennae and it's from the main ISO block so something internally? I'll plug in another radio and see if that has a high draw too.

But my radio functions perfectly so not sure how this is an issue...
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biffer
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Tue Mar 14, 2017 12:17 pm

yo'ud think a turned-off radio would only draw enough juice to keep memory alive.
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Kryptonite
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Tue Mar 14, 2017 1:02 pm

Yes.

Becker tech support confirmed a current draw of micro-amps when switched off.

It's obviously faulty - and uneconomical to repair. :x
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Brianmoooore
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Sun Mar 19, 2017 10:57 am

Sorry, been neglecting this thread!
So what's the total drain now, with the radio disconnected?
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Kryptonite
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Sun Mar 19, 2017 5:37 pm

Hi Brain.

It's 13.6mA
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Brianmoooore
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Sun Mar 19, 2017 7:33 pm

That's about right. How about the other problems you referred to?
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Kryptonite
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Mon Mar 20, 2017 8:57 am

They're all sorted.

The drain is now traced to the stereo but it functions totally perfectly and the manufacturer states a standby current draw in the Micro Amps.

It could be the crossovers? I will try another stereo - if that also has a similar draw then it must be something before or after the head unit itself?
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Kryptonite
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Tue Mar 21, 2017 4:21 pm

This is really starting to piss me off. I did another round of testing.

WITH NO STEREO FITTED

Fuse 21 and 27 fitted = 103mA

Fuse 21 removed (27 fitted) = 134mA

Fuse 27 removed (21 fitted) = 104.4mA

Fuse 21 and 27 removed = 4.40mA

The only common element is the stereo - F21 powers radio memory and F27 powers the actual radio.
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Contours
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Tue Mar 21, 2017 11:55 pm

I thought that Fuse 12 powers the Radio--ignition live position, Fuse 27 powers the Amp--hot at all times and Fuse 28 is for the electric aerial--hot at all times.
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Brianmoooore
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Wed Mar 22, 2017 12:02 am

Contours wrote:I thought that Fuse 12 powers the Radio--ignition live position, Fuse 27 powers the Amp--hot at all times and Fuse 28 is for the electric aerial--hot at all times.
And you are correct - assuming things are wired as BMW intended. Fuse 21 supplies the memory power for the radio.
Does this radio installation have a separate amp?
What are the colours of the BMW wires connected to the radio?
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Kryptonite
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Wed Mar 22, 2017 7:47 am

There's no extra amp. There are a pair of small passive crossovers wired between the stereo and the 3-way component speakers.

The power is supplied using the standard and correct E30 loom direct from the accessory panel.

The E30 Fuse diagram floating around online shows F27 includes 'sound system' - ?

I also tried a brand new stereo and got over 100mA draw at standby / IGN off suggesting the stereo is not the fault.
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Brianmoooore
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Wed Mar 22, 2017 10:12 am

There's no connection from fuse 27 to the radio section of the accessories socket. It is present at socket H though, which is the pin immediately under the radio section
When you disconnected the radio for testing, as in your post on Tuesday, did you unplug at the accessories socket or at the radio?
On most E30s, fuse 27 only supplies the central locking system. The other things listed are relatively rare optional accessories, but there is one where fuse 21 and 27 come together. That is an interior light switch off delay module, fitted inside the RH sill, under the speaker, next to the locking ECU, but it's difficult to see how this being faulty could cause your problems, and even more difficult to see how disconnecting the radio could affect things.
Another option that has connections to both circuits, is the OBC that replaces an analogue clock, but the 27 supply is only used to power the CODE alarm.
The wiring from fuse 27 is red/black, so carefully check for any connections from a wire of this colour to anything radio related.
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