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300tdi Alarm Problem - Siren BBUS / AMR4974


JDB
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Hi - after some advice the Alarm system Siren BBUS / AMR4974 located on the front drivers side wing sounds if it is connected, the rest of the alarm system seems to work ok with it disconnected - but obviously no siren.

Am I right to presume that the internal battery has died and as a result it causes the alarm to sound?

I don't suppose there is a way of testing apart from swapping out, and it looks as though its sealed to stop tampering - so I cannot add a new nicad to it?

I had a quick look but could not find new ones just other used ones - likely to have the same problem in due course?

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I don't think so.

Possibly the BBUS has been activated by disconnecting the main battery (or battery going completely flat) or the BBUS was disconnected without flicking the ignition switch ON/OFF and then unplugging it within 15 seconds.

So first thing to try is reconnect the BBUS and then turn the ignition switch to position II. That should reset and silence the BBUS.

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The sounder needs a 12v supply voltage to 'hold off' and to charge the integral battery. You may not be getting the 12v at the rear plug of the sounder and so the alarm is sounding via it's own battery proving thats ok, and which it is suposed to do if the vehicle battery was disconnected.

Have you tried disconnecting the vehicle battery first then connecting the sounder?. But first follow the rules for disconnecting the battery as shown in the Owners Handbook ie. turn the starter switch 'on' and then 'off' and then disconnect the battery within 15 seconds.

My sounder battery has been dead for years and never given any problems with the alarm system. You can open up the sounder and replace the battery if you ever wish too.

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The sounder needs a 12v supply voltage to 'hold off' and to charge the integral battery. You may not be getting the 12v at the rear plug of the sounder and so the alarm is sounding via it's own battery proving thats ok, and which it is suposed to do if the vehicle battery was disconnected.

Have you tried disconnecting the vehicle battery first then connecting the sounder?. But first follow the rules for disconnecting the battery as shown in the Owners Handbook ie. turn the starter switch 'on' and then 'off' and then disconnect the battery within 15 seconds.

My sounder battery has been dead for years and never given any problems with the alarm system. You can open up the sounder and replace the battery if you ever wish too.

Well just tried the "correct" way of disconnecting the battery, then reconnected BBUS, reconnected battery, siren sounded and would not switch off the way recommended in the book - ie remote fob then turn ignition to position II.

So open to suggestions for something else to try.

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After connecting the sounder it sounds, but if you disconnect the vehicle battery will it stop, this means that the sounder battery is faulty but that will not affect the system.

In theory if the sounder has a fully charged battery you could be unplug, unbolted and removed from the vehicle and walk down the road with it still sounding.

It's possible that the alarm ECU is in an alarm mode and needs to be reset or has locked up in the alarm mode or may be faulty and they do go faulty as they are powered up 24/7.

I don't know how you can tell that the alarm is working other than looking at the indicators flash, then setting it off, but then you need the sounder connected.

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You can tell it's not an alarm problem by testing pin 3 on the BBUS connector. The alarm system grounds the signal on that pin to tell BBUS to go crazy. So the absence of a ground signal on pin 3 means the alarm isn't the cause for BBUS sounding.

The 3 minutes test with the BBUS connected tells you if the sounder has had it or not (backup battery leaked, water ingress etc).

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You can tell it's not an alarm problem by testing pin 3 on the BBUS connector. The alarm system grounds the signal on that pin to tell BBUS to go crazy. So the absence of a ground signal on pin 3 means the alarm isn't the cause for BBUS sounding.

The 3 minutes test with the BBUS connected tells you if the sounder has had it or not (backup battery leaked, water ingress etc).

OK looks as though the "3 minute test" is next - its now 930pm so I think I will leave it until the morning! Will report back - thanks to all for advice so far.

One other thing I think the system is generally OK, with the BBUS disconnected, if I leave the dogs in the car and use the remote (rather than the key in the door to switch the ultrasonics off) the dogs movement triggers the lights to flash as though the alarm is sounding (obviously no siren).

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OK - followed the advice - connected it all back up. Alarm sounded but did not stop after 3 minutes. Tried remote on/off, ignition on/off a few times and it still did not go off. Then whilst doing this and opening and closing the drivers door whilst deciding whether to disconnect the battery it went quiet! Not sure exactly what order I did everything in - problem remote on/off a few times, opened door, ignition on/off a few times, shut door to loosen battery ready to take off, then ignition on/off ready to disconnect.

Any ideas have I reset it? I have wrapped it in rags so that if it does go off in the middle of the night it won't disturb too many people - as I don't have 100% confidence in it being right yet......

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Just noticed what herpmad has posted on another post that is currently running ref a TD5 immobiliser -

had a simlar problem with my disco 1 and funnaly a celio a few years back after i drove it out the show room and the aa man told me a very simple solution which may help

open the door turn key in ignition take the key out slowly (to fast dosnt give it chance to disingage propperly ) then pop the bonnit take off the negative battery lead and leave it off for 20secs then reconnect lock the doors with the fob then unlock and start the key when putting key in the lock do it slowly and turn it one stage at a time

this hole processes resets the imobilser

Maybe this is waht I have done to reset mine?

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Ok hopefully the system is back to normal and will function correctly from now on. If so, sometime in the future disconnect the vehicle battery and if the alarm sounds you will know the the integral battery in the sounder is ok.

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Ok the latest update, the siren has not gone off of its own accord, so today decided to run the "test procedure" which I found on the RAVE CD - ie the release bonnet switch, turn ignition on, open drivers door, ignition off then on.

It entered the test procedure and all the senors worked, but the siren did not go off - indicators and LED all flashed as they should. Thought this was a little strange, so reset alarm, and then tried it in the full mode - and no siren. Looking more and more as though the BBUS is the problem area - time to find a cheapish one to swap out.

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It's my understanding that the test you did is for the alarm system with the one button fob only. The two button fob system does not have a similar test.

I have a 2 button remote and it worked as a test.... for all the systems?

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