My '89 525i developed an alarm problem 4 years ago -- the alarm horn was bipping intermittently
whilst driving & it got worse over the next 2 years. During a routine dealer maintenance the car wouldn't idle unless (any) door was open.
(Door pressure switches are original).
Dealer finally suggested the frontmost module under the rear seat was faulty.
(This module operates the sunroof/electric windows etc. & all work perfectly).
Module was tested (independently)... "no prob". I eventually replaced it with another 2nd hand one & it went good for 2 years.
Now the problem is worse, & as before, only when the car is at full operating temperature, so even after a few miles it starts to bip & the engine will cut momentarily.
Whilst driving it beeps on & off & hazard lights flash... not good to drive around town... or anywhere.
ALSO, whilst still hot, & the car left parked (locked or unlocked), the alarm will suddenly go off.
Opening any door/trunk will stop it, but it commences again as soon as the door is closed.
Turning the key in the door lock several times will sometimes stop the alarm when the door is eventually opened.
BUT SOMETIMES... the alarm will sound WHEN AN UNLOCKED DOOR IS OPENED!!! (Confused so far... yep, so am I).
Otherwise, leaving a door/trunk opened until the car cools down seems to eventually stop the alarm from sounding, then it will sit for days without a murmur! Yesterday after a trip, whilst it was sounding... I removed the module & the alarm kept sounding! I've owned the car for 17 years, & there's no immobiliser that I know of.
For further confusion, fitting the 'offending' module to another car it works perfectly!!!
The dealer can't find a prob & 2 X INDEPENDENT AUTO ELECTRICIANS, DITTO.

SOLUTION: pull the carsh alarm module in the fuse box and drive around and see what happens.
In this case removing the alarm module and reseating it cleared the problem -- dirty contacts!

For more information, its the brown one, crash alarm geber written on it, you cannot miss it


http://www.nmia.com/~dgnrg/page_22a.htm

I had a problem that my hazzard lights came on by their own, it was also this relay. And read this
http://www.bimmerboard.com/forums/posts/410301/

operation of crash alarm

http://www.bimmerboard.com/forums/posts/641230
copied from the net:
Self activating flashers
Self-activating flashers. An owner of a 1993 BMW may complain that the emergency flashers come on by themselves and can't be shut off with the flasher switch.
BMW says this may be caused by a bum transistor in the crash control module, which you need to remove.
It's a tall brown case stamped with the words "Crash-Alarm-Geber." Check the manufacturing date stamped on the side in white.
The first digit of the code indicates the year ("3" means 1993). The second and third digits indicate the week of manufacture (for example, "08" means eighth week).
If the unit was built before the eighth week of 1993, replace it. Use Part No. 61 35 1 384 761 for 318i, 318iS, 325i and 325iS models.
Use Part No. 61 35 1 384 732 for the 525i, 530i, 540i, 740i, 740iL, 750iL, 840Ci, 850Ci and 850CSi.

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