Alarm keeps going off

[Ed Addis]

1999 Carrera 4

This weekend the alarm has started going off at seemingly random times after locking the car. Sometimes this is within a minute or so, and other times after maybe an hour or two. I've tried going round checking the closure of all the monitored points (doors, boot, bonnet, oddments tray etc), but can't seem to stop it. At the moment I'm having to leave the car unlocked, which is worrying! Is there anything I can do myself or is this automatically a job for a garage? Is there any way of disabling the alarm, so I can at least lock the car until it's sorted?

Thanks

Ed

 

[Richard_Hamilton]

Check the tilt sensor, which on your car is located next to the battery, under the alarm siren. They have a nasty habit of filling with water, causing false alarms.

If that isn't it, then the next most likely thing is the interior monitoring sensor. If you get a diagnostic check done, it should show what is causing it.

Edit: You could try unplugging the tilt sensor. Also, if you double-lock the car with the key or remote, it will disable the interior sensor.

 

[Ed Addis]

Thanks very much Richard. I'll try these when I get home.

Regards

Ed

 

[Ed Addis]

Had a look at the tilt sensor, but nothing much to see - the car had dried out pretty well by then. I think this is the most likely solution, however - both the recent episodes of this problem have coincided with wet conditions. The alternator failed recently and fried the battery - both have been replaced, but the battery tray seems to have a lot of dried up corrosion residue and I suspect that drain holes may be blocked. Is there any problem about removing the battery, to get proper access to the tray? I have the code for the radio, but is there any other issue with disconnecting for a while?

Many thanks

Ed

 

[Richard_Hamilton]

Before you disconnect the battery, switch on the ignition (but don't start the car) and turn off all the items you can. (Aircon, radio, interior lights, etc). Leave the key in that position while you disconnect the battery, negative terminal first. This will stop the alarm siren going off, as it has a backup battery inside.

DON'T lock the front compartment with the battery disconnected. Also, you won't be able to secure the car, as the passenger side won't lock without the central locking system.

 

[Ed Addis]

Many thanks for this info. It's clearly as complicated as I feared! Will probably have a go at the weekend.

Regards

Ed

 

[Ed Addis]

Sorry for the delay in posting again.

I removed the battery and then the siren and tilt sensor assembly, and decided that the latter had water in it (it's semi-transparent). However, I couldn't find any way to remove it from the mounting bracket, without damaging it, so I ended up just disconnecting it, as others have - that wasn't easy, as the connector seemed to have 'welded' itself to the socket. This appears to have solved the problem as I've had no more problems with the alarm.

Many thanks for your assistance.

Ed