Alarm Sounds when plugged in

Hey guys, hoping for a little help please

I bought my Discovery 1 about 9 months ago and the alarm siren has never worked. It didn't really bother me so I never tried to fix it. I'm off work for 2 weeks now so thought I'd have a look at it..

The alarm on the car seems to work perfectly fine. As in you lock the doors with the 2 button fob, the doors all lock, and the hazards flash a few times. If you then open the door with the key, or anyone is moving inside when you lock the car (a dog for example) the hazards start flashing as if the alarm is going off. However, the siren doesn't sound.

I went looking for the siren and discovered it on the driver side of the engine bay but it was unplugged. Now this is the odd part, when I plugged the siren in it goes off. (I bashed my head of the bonnet it made me jump that bad! ) The hazards aren't flashing or anything and it doesn't matter if the car is locked, unlocked, doors are open/closed... It just stays going off.

Anyone got any ideas about what could be causing this? Is it the siren itself or something electrical further back? If you need anymore information on the car let me know as I'm stuck..

Thanks in advance,

Rob

There's a backup battery in the siren that goes faulty apparently, and makes the siren sound. Disconnecting it shuts it up. That's as much as I know, but mine is also disconnected, so I'm expecting to have the same problems as you very soon!

Very common problem with the disco, most are unplugged now. I understand the only way to fix them is to replace the spyder which is bolted to the bulkhead but you need to remove the dashboard to get to it. I have been told there may be a way to rest it by pressing the lock/unlock on the remote in a sequence (code) which would have been issued with the motor when new or may be available from the supplying garage but as all these are now old motors nobody seems able to confirm this

What's the spider got to do with it? As I understand the spider is part of the immobiliser and just isolates the starter solenoid and fuel solenoid, and has bugger all to do with the alarm?

EKA code surely isn't required, if the alarm works and car starts without the siren connected, I would have thought it's just a case of repairing/replacing the siren and plugging it back in. If there was an underlying problem with the alarm you'd have the indicators flashing all the while

TheKeymeister said:

What's the spider got to do with it? As I understand the spider is part of the immobiliser and just isolates the starter solenoid and fuel solenoid, and has bugger all to do with the alarm?

EKA code surely isn't required, if the alarm works and car starts without the siren connected, I would have thought it's just a case of repairing/replacing the siren and plugging it back in. If there was an underlying problem with the alarm you'd have the indicators flashing all the while

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For all intensive purposes, the alarm SYSTEM works exactly as it should. It goes off when it should, immobiliser works etc. The alarm SIREN is what appears to be broken. So I'd have to agree. But then again, Im usually wrong

yup a bit of dis-information there, and neither is it a very common problem.

In a fully functioning sounder it may sound when connecting the 12v supply to it, but it can be silenced by pressing the fob button.
As yours can't then the relay inside the sounder maybe faulty (stuck on) likewise the PCB may also have a fault may be damaged by water.

The best thing to do is bin the sounder and get a replacement, if you want a sounder that is.

It's a link to a different forum, but this is the thread I base my assumptions from

300tdi Alarm Problem - Siren BBUS / AMR4974 - Discovery Forum - LR4x4 - The Land Rover Forum

I had this problem and the back-up battery pack had given out and has seeped onto the pcb, making it sound when connected.

lorri789 said:

I had this problem and the back-up battery pack had given out and has seeped onto the pcb, making it sound when connected.

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Odear, i'm lucky then, my battery has been flat for a long while, 11 years maybe but can't ever see that a towrag would cut the vehicle battery cable to disable the alarm and therefore set off the BB sounder.
It's a Thatcham thing to meet their vehicle security spec..

I bow to any body with greater knowledge than mine, i'm only passing on info given to me by an alarm engineer, mine appeared to have the same probs as yours, i have been known to be wrong once before as my missus will tell you lol

cheers for the help guys, ill see about getting a replacement sounder. May as well do it if they're not too expensive