On my 87 735 you can lock the front doors in 2 ways - turning the key thru
45 degrees locks doors but allows opening from the trunk, whereas turning
key thru 90 degrees 'double locks' it and then the trunk unlock doesn't
work.

On one particularly blue Monday double locking the doors while one was open
and then merely shutting the door confused the system totally - it wouldn't
open at all! Two BMW technicians took over 2 hours to get it open again
despite simulating a crash (thumping the floor-mounted sensor with a lump
hammer) and hot wiring the engine!

J.

electronic unit situated behind the stereo speaker in the front driver's
footwell. ( I am British so it is possible that your unit is behind the
passenger footwell -  right / left hand drive - you see ) . After a number
of years they have a habit of failing and the central locking develops a
mind of its own. It is possible to by pass all of the electronic control by
just physically disconnecting the electronic system ( until you get around
to replacing the control unit - which may be expensive?? ). It is a bit of a
pain but you need to remove the door interior trim and unhook the solenoid
actuators for each lock. Just un - screw / un - bolt  them and un - hook the
wire loop that connects them to the lock itself ( don't forget the boot
( ok - trunk! ) and the fuel filler cap - which you can get at from behind
the carpet  / trim in the boot ( ok - tunk!! ) ). Each lock can now be
operated independently using the key. You do not, of course,  have central
locking or dead locking ( called by BMW - double locking ) but at least you
can get in and out of your car!!

I know this because it happened to me. One a number of occasions the doors
would lock and unlock repeatedly for no apparent reason. Hpe you can get it
fixed.

David Matkin.

I just got finished working on my door locks. The locks all work by
mechanical linkage connected directly to the key.

Each lock also has a switch that when activated will operate a motor on each
of the other locks to either lock or unlock the lock as is apporpriate. The
electrical locking and unlocking is controlled by a central controller, and
if the electrical lociking and unlocking is toast, then the problem is most
likely in the controller. But, if the electrical locking and unlocking works
from some locks but not others, then I'd have to suspect the switch on the
offending lock.

I have a '94 convertable -- same operation as the coupe -- and the windows
are supposed to drop a bit when the door handle is lifted. My drive side
door failed to drop the window unless I operated the latch by hand and
allowed it to slam. The switch that controlled this operation was dirty --  
not surprising after 12 years -- and needed to be cleaned. The switch itself
was okay, but the linkage surrounding it was gooey. I have to think that
your switches are gooey in much the same manner, OR the controller has taken
a bye.