Draining my battery

[ProToZyKo]

Suddenly got a problem with a drain in my system. I have figured out that fuse 27 is causing the damage.
From what i can see central locking, door lock heating, OBC and horn is using this fuse.
The drain is around 4 AMP and what can use so much all the time? Central locking is working so i can´t see any problem there, same with my horn.
What else? door lock heating? I wan´t to have this function since my locks keep freezing in the winter.

[RegTourist]

I have the same problem........do you have a BMW alarm fitted, as I think this is what is causing mine! If anyone knows why the alarm will sap so much juice from the battery ..please let me know?
Reg

[ProToZyKo]

A little more info.
Friday i smelled something burning, didn't last long and i didn't figure out where it was coming from.
Now i have taken the fuse out and the only thing not working is central locking, why is horn and audio working? What else is using the fuse?

I have alarm but this one is working without fuse 27 so it's not causing the drain.

ReqTourist is it the fuse that goes to the alarm that is draining? Have you measured your drain?

[Brianmoooore]

Horn fuse is 7, so not relevant to this. The horn connected to fuse 27 is the alarm horn, which is part of the CODE function of the 13 button OBC.
Similarly, the fuses for normal radios are 12 and 21 - 27 was only used with the more sophisticated systems with seperate amplifiers.
Central locking, and the door lock heater (if fitted) are the only things normally on 27, but the fuse is also attractive to ICE installers!
Does the central locking work if you replace the fuse? Open a window before you experiment.

[ProToZyKo]

Central locking works as it should. Im thinking my door lock heater is stuck on. Any suggestions on how to fix it?
What i have found out by some googling is that when i lift the door handle it should start the heating of the door lock, but sometimes they fail and stay on all the time.

[Brianmoooore]

Take the door card off, remove the plastic film, and disconnect the heater - there's a plug and socket in the lower part of the door, under the latch assembly.
Check the battery 'leakage' current then. I've no idea what sort of current a door lock heater draws, but 4A is a reasonable figure, so your theory may well be correct.

[ProToZyKo]

I will, thinking it must be destroyed by now, it takes around 45 hours to drain both of my battery's with a draw of 4A ;)

[Brianmoooore]

If you no longer require the lock heater, do the well documented "red/black wire" modification.

[ProToZyKo]

I do require it, have had allot of trouble with the door in winter time, was hoping it would work this winter since i fixed the contact, but then the heater broke.
Wouldn't disconnecting the heater be a better alternative to the "red/black wire" mod?

[Brianmoooore]

Wouldn't disconnecting the heater be a better alternative to the "red/black wire" mod?

It would cure the battery drain, if the lock heater is at fault, but still leaves the two corrosion promoting permanently live pins in the door loom plug/socket.

[ProToZyKo]

Unplugging the heater stopped the drain.
How does the heater work? Would be nice to fix it.

[Brianmoooore]

The actual heater replaces the large C clip that holds the lock assembly in place.
AFAIK the actual switch that controls it is a rather crude blade arrangement bolted to the external handle. Should be obvious what's happened to it by examining it while operating the door handle.

[ProToZyKo]

Seems like it's always on here. Think the black relay thingie is broken Well i can try this winter without it, now i have central locking maybe things will work better.