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hi, a couple of months back we went to dublin from liverpool whilst in dublin one morning the central locking failed with the remote key fob i pressed the boot unlock and it worked but when i opened the boot the alarm went off and i had to disconnect the battery when i connected it again the alarm went off again - i used the key to unlock the doors when putting the key in the ignition the alarm stopped and the car started.
i have changed the batteries in the key remote, i have tryed to re anyalise the key but the key remote fob still does not work but the central locking with the key works - the alarm does not work the light on the mirror does not flash anymore.
the key in the boot does not unlock the boot or anyother but the drivers door locks the boot.

any help would be much appriciated on fixing this.
thankyou for your time.
 

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Don't know if this helps as I might be stating the obvious which you may have already checked. I can only offer you non expert logic plus a reasonable amount of car/ life experience.

So having made the 'please don't hit me if I'm being patronising' statement;

I just bought a '98 540i. I noticed that the mirror telltale light wasn't flashing although the central locking worked normally from the key fob and the indicators flashed when locking the car this way. Above the battery (in the boot in mine) is a fuse bank. On closer inspection I noted the fuse actually missing from the bank labelled alarm and fitted one. The mirror telltale now flashes as it should.

Only reason I say this is because if you have a blown/missing fuse, replacing it and seeing what happens would at least possibly eliminate one fault which may be confusing the issue. Don't know your model or year but probably similar design logic behind the alarm/immobiliser system.

From my owners manual (covers 1998 528i and 540i);

To activate and deactivate the
alarm system


When the vehicle is locked or unlocked
with the key or the remote control, the
alarm system is also simultaneously
armed or disarmed.

Central locking system

With the key

One turn of the key in the driver's door
lock unlocks the driver's door only.
Turning the key a second time unlocks
all of the remaining doors, the luggage
compartment lid/tailgate and the fuel
filler door.

Have a good look at the sections in your manual covering keys, central locking and alarm.

Can you lock and alarm the car from the key fob? If so, the 'open' button on the fob could be your problem.

Opening the boot with the car locked will set the alarm off. If you subsequently then unlock the drivers door with the master key and start the car the alarm stops. To my understanding both these things are normal and desirable security.

If you eliminate the minor and/or obvious causes and establish that the alarm and central locking are working normally when you don't use remote opening, then the 'open' button on the fob is a suspect.

Is there a telltale led on the fob and if so does it light when you press open? I've had remote fobs where the button contacts degrade over time and cause intermittent function depending on how hard you press. If you can open the fob eg to change the battery, then you should be able to see and check/clean the internal button contacts as well.

All of this assumes your car system is similar to mine. Hopefully one of the real experts on here will be able to tell you exactly what's wrong in one sentence.

Hope some of this helps. :)
 

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Would also be worth checking the wiring on the boot, where it exits the vehicle and enters the boot, repeated opening and closing breaks the wires.
 
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