help, xantia alarm will not turn off!

[aerodynamica]

Help, curiosity got the better of me! Since I got the car the alarm siren has been switched off via the key switch at the scuttle. I decided to switch it back after some crim picked the locks few months back. The alarm has been set by remote and unset each time since with no probs. I decided to set off the alarm to test that it actually sounded by opening the door. It went off fine. I went to switch it off with the ignition switched on and the override pressed where the usual flashing indicators activated but the siren kept on! Next time I tried it the override button did nothing! No flashing indicators.
It will not go off either opening and closing the doors with the remote, key in ignition and the override, or switching the siren off via the key barrel on the windscreen scuttle. It's like HAL. I pulled out fuse 17 and the siren went to half the volume. It fades to silent with the ignition off as though some second battery isn't doing its job, but comes back after ignition on. Disconnecting the battery kills it altogether.

Help!

[jgra1]

I can tell you where the siren is if you are really stuck Graeme?

[aerodynamica]

I think the siren is inside the lh wing so not readily reachable.

I'm keen o finding out why niether the OFF button or the key switch don't work. I wonder if the key switch can only put the siren off (leaving rest of alarm functional) before the alarm is tripped but not during. Doesn't explain why the key in ignition and off button do nothing now.

Does anyone know what the button on the dash to switch off actually does? I mean is it sending a logic signal to alarm unit or is it a physical switch? Same with the key switch thing under windscreen.

If needed, how can I find and remove the alarm ecu? I don't see anything under the passenger seat.

[myglaren]

Doesn't the dash button just disable the volumetric sensors on a one time only scheme - next time the car is started it reverts to normal?

[red_dwarfers]

A little alarm FAQ:

Disabling the volumetric protection - with the ignition off and the alarm disarmed, press the button for 2 seconds. The warning light will light continuously. Lock the car and set the alarm. For this one time, the alarm will only monitor the doors, bonnet and boot (perimeter protection).
While the warning light is continuously lit, if you decide that you do actually want volumetric protection on top of the perimeter protection, press the button again for 1 second.

Disarming the alarm without the remote control - Unlock the doors with the key. Within 10 seconds of the siren sounding, press and hold the button whilst turning on the ignition. If necessary, repeat if the siren restarts after 30 seconds.

Preventing the alarm from being armed without the remote control when connecting a battery - with the battery disconnected, turn the ignition on. Connect the battery. For this one time the alarm will be disarmed, next time the battery is disconnected the procedure will have to be repeated.

Preventing the siren from sounding when the alarm activates - Only applicable to Xantias until around '95/'96. Locate the switch under a cap by the N/S of the scuttle. Turn the switch using the key. The alarm siren will not sound unless the switch is turned back.

With the turning off the alarm using the button and ignition thing, are you keeping the button held in before, during and after turning the ignition on?
It's interesting to hear that locking/unlocking the car on the remote doesn't stop the alarm!

On the off chance, you don't have any water under the front or rear footwell carpet on the passengers side do you? I've had experience with that causing odd issues with the alarm...assuming on the early Xantias it is there! If I remember rightly, on my '97 it is fairly well tucked away under the carpet.

[aerodynamica]

Hi Kev, thanks. Just to address the issue:

Disarming the alarm without the remote control - Unlock the doors with the key. Within 10 seconds of the siren sounding, press and hold the button whilst turning on the ignition. If necessary, repeat if the siren restarts after 30 seconds.

- this is the stage where it went wrong, in the past this has worked fine but carrying out this didn't silence the alarm (though the headlights stopped flashing) the second and third times I tried it after getting out, opening the door again, key in and button held nothing happened - usually the indicators flicker 3-4 times but this didn't happen.

Preventing the alarm from being armed without the remote control when connecting a battery - with the battery disconnected, turn the ignition on. Connect the battery. For this one time the alarm will be disarmed, next time the battery is disconnected the procedure will have to be repeated.

Funnily enough, this is what I did last night and this morning the alarm seems to have been deactivated. I haven't replaced fuse 17 yet as I'm so busy trying to get the CX on the road in time for the ICCCR rally!

Question: is there a 'backup' battery for the alarm? as the alarm still sounded after I pulled out fuse 17 but got quieter until it was barely audible. I wonder if it was running on a duff back up that only lasted 5 min.

[red_dwarfers]

I think there is a backup battery, can't say for sure at the moment. I've got some wiring diagrams so will have a look tomorrow.

I remember reading somewhere that low or fluctuating voltage can set the alarm off. Saying that though, it wouldn't make sense here as the alarm is already going off.

I would disconnect the battery, stick the fuse back in and try the whole ignition on, connect the battery routine just to make sure the alarm still does deactivate.

Going back to this bit:

I wonder if the key switch can only put the siren off (leaving rest of alarm functional) before the alarm is tripped but not during

I would test to see if this is true or not.

If it is true, it rules out the under bonnet switch.
If it's not, it could be the switch, wiring or alarm ECU. But if this and the dash button stopped working at near enough the same time, it's likely the problems are related so then I would have thought the only common factor is the alarm ECU or wiring before it splits off.

Leading on from that, it would be worth testing to see if the button on the dash is definitely talking to the alarm ECU by holding in the button for 2 seconds and seeing if the light stays on continuously.

If it doesn't then there is likely a problem with either the button, wiring or alarm ECU. If it does, it rules out the button and wiring.

Looking forward to seeing the CX at the ICCCR!