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Here's Chris's Central locking FAQ

Subject:  Door locks etc
From: Chris Pawlowicz 

>I purchased a 86 325e last fall, and since then I have had a nagging
>electrical problem.  The details are as follows:
>1.  The problem is a constant current draw which would draw down my
>battery, and after a week away from home, the car would not start.
>2.  The drivers side interior light has not worked since my purchase.
>3.  I did not realize that the car has central locking

Ok.. there are a few things you can do and check -

first, you can get your hands on the Bentley manual for E30 cars.. it
has lots of good stuff including wiring diagrams etc. Not perfect but
a big help. It costs about $40 usd or I found one in my local library
and photocopied the electrical stuff. Ooops, that's illegal. I
wouldn't do that!

One possiblity for current draw is you *might* have an electric lock
heater. In the winter, if your locks are frozen, many E30's had a
feature where you lift the door handle and this turns on a lock heater
to unfreeze the locks. Problem was lots of these heaters stay stuck
*on* and either a) drain the battery b) start a fire! c) burn
themselves out. You have to take the door apart to get at it.

A good place to start checking for current draw and lock operation is
at the connector between the A pillar and the drivers side door. There
is a rubber boot covering a 22 (?) pin connector - this has all the
connections for the door locks, the power mirrors, heaters, etc.

This connector is very probably very ugly looking with
rust/corrosion/guck. If so, this is very probably one of the main
sources of your trouble.

Having the Bentley book here will help - there are lots of pins and
you can test all kinds of stuff here.

Unfortunately actually testing the door lock operation with the door
open is not possible. But you *can* check stuff like current draw to
various heaters etc. as well as visually check all the pins.

To get at the car side of the connector (as opposed to the *door* side
of the connector) you need to take hood release off (release the hood
first in case you want to mess with the fuses!) then the speaker, then
the kick panel. Then you can push the door side of the connector *in*
from the door area and pull it out from the inside of the car.

Note that messy pins in the connector will often lead to
randomly working or not working central locking, interior lights,
'double lock' feature, mirrors and window problems.

I recently changed a bunch of pins to get my stuff all working again -
it was really annoying when the only door I could open was the drivers
door because the rest of the car was 'double locked' !

I got replacement pins from my mechanic (who gets them from BMW)
but I know that Newark Electronics (1 800 4NEWARK) sells the same
things. Unfortunately they sell in bags of 100 :( but there might
be electronics stores in your area that can sell you the pins.

They are pins from AMP for their CPC connectors..
and will cost up to a couple of bucks a pin. You will 
probably only need a few.

Pull a pin out of the connector, cut it off, strip some wire, solder
in a new pin, and push back into the connector.

I only had to replace two pins (the others were fine) to get all my
locks working properly.. (they had been getting possessed/erratic). My
interior lights were also possessed.. you could hear the central lock
relays clicking away deep in the kick panel area trying to figure out
what to do.

Which brings up the relays - they are located way *down* in the kick
panel behind the speaker - along with the central lock computer (?). I
didn't need to mess with this so I never pulled it out. 

hope this helps!
chris pawlowicz (
'89 325i


From: (Paul R. Reitz)
Subject: E30 central locking (long)

To those of you who requested additional info on the E30 door locks:

E30 Central Locking Operation

The following description is based on the 1990 325 iX Electrical
Troubleshooting Manual (ETM).  It probably works the same way on related
models, but I make no representation of the range of applicability.  If you
find it does not to apply to your E30, please contact me via e-mail at
 with particulars.

A Macintosh PICT file of the CLCU and basic wiring is available that can
help make sense of the following descriptions.  If you can receive MIME
attachments and want the diagram, let me know.


- Terms are those used in the ETM, except "unlock inhibit" has been
replaced by double-lock".  Don't confuse "key lock" with "door lock" or
door latch.

- The ETM does not describe what goes on in the central lock control unit,
so I cannot infer the exact voltage level required to assert a function,
input impedances, or other electronic behavior such as output durations,
etc.  The double-locking function likewise cannot be determined exactly
from the ETM, but it can be deduced.

- The manner in which the motors, cylinder locks, door latches, locking
mechanisms, and linkages operate may not be adequately depicted in the ETM.
Further, I have made no effort to verify the ETM's depictions.


CLCU:    Central Locking Control Unit - the electromechanical assembly,
behind the speaker in the driver's kick panel, that accepts electrical
inputs to lock, unlock, and double-lock the doors, and that contains the
lock and unlock relays and the impact switch.

Door lock motor: operates the door lock, the mechanism that prevents the
outer door handle from opening the door.

Double-lock motor: a motor that operates the (unlock inhibit) mechanism,
which prevents the door lock button from being raised.  This mechanically
prevent doors unlocking.  The driver's door does not contain a double-lock
motor, according to the ETM.

Key lock: the key-operated cylinder lock that mechanically operates the
door lock and other electrical switches.

"Unlock inhibit": the ETM term for the double-lock function.


-       The rotation of each door or trunk key lock does two things:
operates mechanically on the lock for that door (or trunk), and operates
one or two switches that ground one of three "inputs" on the CLCU: Lock
Request ("lock"), Unlock Request ("unlock"), and Unlock Inhibit Request
("double-lock") .

-       Not all key locks switches can operate all input functions.   For
example, the passenger's door and truck key locks  do not operate the
double-lock function.

-       Certain functions are mechanically prevented.  For example, if the
double-lock feature is engaged, the passenger's door key lock (on a '91 iX)
will not mechanically operate, and, therefore, cannot issue the unlock
command to the CLCU.

-       The lock (CLCU pins 7 or 8), unlock (CLCU pins 6 or 9), and
double-lock input (CLCU pin10) are switched to ground to activate each

- Locking and unlocking apply voltage (of opposite polarity) momentarily to
the door lock motors.  This is accomplished using two "1 pole, 2 throw"
relays in the Central Locking Control Unit, labelled "lock" and "unlock".
The common contacts of these relays (CLCU pins 1 and 2, respectively) are
connected to opposite sides of the door lock motors.  (The lock relay
common, in addition, connects to one side of the double-lock motors.) The
normally closed (NC) contacts of both relays go to ground (via CLCU pin 4),
and the normally open (NO) contacts both go to +12 v (via CLCU pin 3).
When either relay is energized, 12 v is applied through the NO contact to
one side of the motor while the other side of the motor is grounded through
the unenergized relay's NC contact.  Only one relay is actuated at a time.

-       The polarity of the double-lock motor voltage is reversed with two
diodes.  One side of the double-lock motors is connected to the "lock"
relay common (CLCU pin 1); the other side of these motors connects to CLCU
pin 11.  One diode, conducting from pin 11 to pin 10, provides the ground
return for double-lock motors when pin 10 - the unlock inhibit
(double-lock) input -  is grounded.  Another diode, conducting from the
unlock relay common (CLCU pin 2) to pin 11,  supplies 12 v to pin 11 when
the unlock relay is actuated.  This applies a reverse polarity voltage to
all motors - lock and double-lock -  with the (unactuated) lock relay
common providing the return to ground via its NC contact.   If you've
followed along, notice that if the unlock function is operated while the
unlock inhibit microswitch is also operated, it will produce a short
circuit from +12 v to ground through the aforementioned diodes, surely
destroying them.  This may be the source of several cautions, both in the
ETM and in the factory repair manual, about not connecting power to the
CLCU "if the unit is not properly positioned"; see CAUTION, below.


When any door or trunk key lock is rotated (45 degrees for the driver's
door), it operates a switch that grounds the "lock" input of the CLCU.
This momentarily energizes the "lock" relay in the CLCU, applying +12 v
(via CLCU pin 1) to one side of all door lock motors which are grounded as
described above, and also to one side of the double-lock motors, which
don't operate, as they lack a ground return path at this time.


When the driver's door lock key (only!) is turned to 90 degrees, it
operates the "unlock inhibit" microswitch, which directly grounds the
"unlock inhibit request input", CLCU pin 10.  This operates the lock relay
and simultaneously provides a path to ground for the double-lock motors via
the diode from pin 11 to pin 10.  Consequently, the double-lock motors
operate, and the door lock motors operate again.


Unlocking any door or the trunk operates a contact that grounds the unlock
request input.  If the car was double-locked, the passengers' door key is
physically prevented from rotating, which prevents unlocking.  The drivers'
door and trunk locks can be operated, however.  When the unlock request
input is grounded, the "unlock" relay momentarily applies 12 v (of opposite
polarity, as described above) to the door lock motors, and, through a
second steering diode, to the double-lock motors as well.  The double-lock
and door lock motors are grounded through the "lock" relay NC contact.
(Apparently the double lock mechanism unlatches quickly enough to allow the
door lock motors to do their job!)


A key point (pun intended!) is that if the "unlock" relay is operated when
the double-lock microswitch is also operated (grounded), it will damage the
two steering diodes in the control unit.  Normally this can't happen - it
would require two keys to be used simultaneously, one unlocking while the
other double-locks.  However, it could happen accidentally during system
diagnostics.  For example, suppose the normally-open inertia switch (which
operates an "automatic unlock request function") has been unintentionally
closed when the CLCU is removed for inspection.  If power is restored to
the CLCU as the driver's door key lock is rotated 90 degrees, pfffttt!

Unknowns / Opportunities?:

The ETM shows the driver's key lock mechanically operates the double-lock
in that door; motors are shown for double-lock only in other doors.  Yet
the ETM diagnostic for the double-lock function, jumpering CLCU pin 10 to
ground, does not make an exception for the driver's door.  This is
consistent with the observation that the unlock function (which can be
generated by the trunk key lock) disengages the double-lock on the driver's
door.  How these occur is not at all clear, but it suggests that completely
*electrical* operation of the double-lock function is possible.  This could
allow remote alarms to also double-lock the car by having the remote
momentarily ground terminal 10 of the CLCU.

By the same logic, it should also be possible to double-lock the car from
every lock by disconnecting the lock input wires from CLCU pin 7, and
attaching them to the existing wire on pin 10. However, what would happen
when the passenger's door was locked??  If the double-lock worked, you may
not be able to  rotate the key lock again.  It's conceivable that a
mechanical link may preclude the passenger door from double-locking while
the passenger door key lock is rotated.

*** There are potential hazards to hard-wiring the double-lock, or any
other home-brew "enhancement"!***  For example, it would not be possible to
lock the car from the outside without locking the car's occupants in.  It's
also possible that rapid operation of a key switch might create an
unintended condition that burns out the CLCU.  I do not advocate casual
alteration of these locks!

Is it a prerequisite that the door locks already be in the locked postion
for proper mechanical operation of the double-locking mechanisms?  The ETM
diagnostic suggests the answer is "no".

The ETM also shows a separate right hand door microswitch used to operate
the lock function, despite a 1P3T switch also operated by the key lock.
This latter switch has both lock and unlock positions, but the lock
position is unused.  The logic behind this setup is not obvious to me.
Perhaps knowledge of the physical layout, etc., might help.

If anyone has further experience with any of the above issues, please send
your results to me via e-mail.


--Paul Reitz (preferred), or