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From digest.v9.n643 Sun Dec 6 19:07:43 1998
From: Chris Pawlowicz <>
Date: Sun, 06 Dec 1998 21:15:07 -0500
Subject: E30 alarms

Ken W sez
>Anyone know what alarms for E30's use the double locking feature? I'm
>actually having a Viper installed at this moment in my '91 M3 and the
>guy, who has owned BMWs and has been doing alarms for about 12 years,
>said that he didn't think the alarm would use the double locking.

E30 (+E28 + other '80s vintage bmws) double lock mechanism works like this:

key turned in drivers door lock cylinder engages a cam/spring arrangement that physically jams the lock cylinder in place.. because it is jammed in place the door lock motor CANNOT unlock it

when the cylinder is in this position it holds down a microswitch which tells the central lock computer to double lock all other doors... other doors include a lock motor that moves the lock mechanism to locked position AND makes another motor that moves a PIN to jam the lock mechanism in place..

  • -the drivers door lock can only be double locked physically with a key
  • -the other doors are double locked electrically from the CLCU

so: no alarm can double lock the drivers door and care must be taken before attempting to electrically double lock the other doors.. (screw up and poof! goes the central lock computer)

It is probably possible to modify the system so that it could be double locked electrically (parts from RHD cars etc) but would probably not be worth it.

Euro/BMWfactory alarm (a la Hott Rodd) is not keyless.. it engages by sensing when the car is double locked (via key) and then turns itself ON

for more central lock stuff or

chris pawlowicz
'89 325i
'74 2002

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