Car Alarm

koppite34 · Post by **koppite34** » 12 Aug 2010, 13:56

My citroen xantia's alarm keeps going off with no-one touching car no gust of wind or thunder and lighting so why it keeps going off any idea's please
Thanks
Mike
P.S. I forgot to mention that my rear passager door stays locked, wont open even when all other's do is this connected to my faulty alarm?

spider · Post by **spider** » 12 Aug 2010, 14:15

First thought, poor ultrasonic sensors.

Not sure where these are (at a guess in the A pillar's)

You can set the alarm and press the )) button to disable these (usually) see if that helps.

I (think) you can actually just unplug them but that may trigger a permanent alarm not 100% sure on that. With 106's, well some of them you could simply unplug the U/S if they caused problems.

Post by **xantia_v6** » 12 Aug 2010, 14:48

Ultrasonic sensors are the most likely culprit.

Some alarms are susceptible to RF, if I left my phone in my 1995 Xantia, the alarm would go off when the phone registered or got an incoming call. My 1997 Xantia does not suffer from that.

landcrab · Post by **landcrab** » 14 Aug 2010, 12:43

My car does exactly the same thing. I would like to remove the alarm altogether but I don't know how.

The ZX had a switch under the bonnet where you insert the key and turn it off. Xantia's are not that clever.

My solution is never to lock the car at all. It has never been locked in more than 4 years. I never leave anything of value in it and nobody has ever touched it as far as I am aware.

After all who the hell wants to pinch an old Citroen? You can't even give them away.

Post by **CitroJim** » 14 Aug 2010, 13:06

Sensors are the very most likely cause but it's also worth checking for damp ingress in the passenger footwell as alarm circuits pass this way and damp can cause false triggers.

The ultrasonic sensors for both marks are in the front door window surrounds and differ between the MK1 and MK2.

In a MK1 you have both the ability to remove the alarm completely (in theory - never done it) and the choice of whether or not you set it when locking up. Sadly neither is possible (to my knowledge) on the MK2 due to how it forms an integral part of the body computer.

Early MK1s did have the defeat keyswitch under the bonnet. It was deleted for the 1997 MY.

You can set the alarm with the ultrasonics defeated by pressing the ultrasonic defeat button ( a loudspeaker symbol with a cross through it) with ignition off until the alarm LED lights up solid. Then lock up and the alarm will set with the ultrasonics defeated. The alarm LED will then flash as normal.

If you press the ultrasonic defeat button to make the alarm LED light solidly, note that you have to lock up and set the alarm promptly, if you don't the defeat request will time out and they will re-arm so it is essential you lock and set whilst the LED is glowing solidly.