Alarm false alarms!

Robin · Post by **Robin** » 01 Jan 2004, 18:58

Hi, can anyone make a couple suggestions on where to look for a fault on the alarm on my October 97 1.9 TD Xantia Estate. All works as it should, the doors close nicely and the interior IR system de energises or energises as it should. However the alarm will sound at any point from 10 minutes to several hours later. A clue may lie in the fact that if the outside temperature drops too then the alarm will sound sooner than if the alarm is set on a nice warm day. Am I looking for a mechanical switch fault perhaps?[?]

edd001 · Post by **edd001** » 01 Jan 2004, 19:03

hi
may help may not help but
i have had this problem on another make of car and it was sensertiverty of the alarm.
if it has an adjuster on it try changing that but be carefull to note where origanal possion is and only adjust it a little at a time.
hope this helps

rg · Post by rg » 01 Jan 2004, 21:38

Can you disable the "cabin motion" sensor?
This detects changes in air pressure. On my XM this can be inhibited. Check in your handbook.
I had a BMW which would set off the alarm as the cabin cooled down and the pressure changed.
HTH
rg

Robin · Post by **Robin** » 01 Jan 2004, 22:32

Thanks for the thoughts. I have tried the system with the cabin sensor off and it does just the same. I was wondering what the system is that detects an opened door - is it a switch or voltage sensor as the interior lights comes on?
Also, could a voltage sensor be so sensitive that it detects a battery voltage change as it settles down after it hs been charging.
Incidentally, can anyone tell me where the alarm system 'brain' is located?[:)]

Kered · Post by **Kered** » 01 Jan 2004, 22:35

Hi Robin
The alarm unit lies under the carpet under the front passenger seat. It seems that it it is an ideal position to get wet from any water leakage and corrosion can sometimes be a problem.
Derek

alex · Post by **alex** » 01 Jan 2004, 22:44

I was just going to make the same comment as Kered - water gets under the front carpet if the trim below the windscreen isn't sealed onto the screen - When I had a similar false alarm problem - replacing the ultrasonic sensors in the front doors fixed it - they weren't too expensive...

Robin · Post by **Robin** » 02 Jan 2004, 00:36

Thanks folks. I guess you can assume I will be crawling about tomorrow. Happy new year![:D]

David Goddard · Post by **David Goddard** » 02 Jan 2004, 02:13

And you may find it's dry. I had the same fault Robin, and gave up with the alarm. Mine has a keypad immobiliser which is a super anti theft device, in my opinion. I unplugged the module (under the carpet, under the passenger seat). Everything else works i.e. double locking, but no alarm problems.

davey · Post by **davey** » 02 Jan 2004, 04:09

Had what sounds like the same prob a few years back with the alarm 'just going off' for no apparent reason. Found that it was the ultrasonics being a bit eager. You can disable this function thru keyfob but u have to do it everytime.
Found it easier to simply disconnect the ultrasonic detector in the passenger door. this cured the spurious alarm sounding but still had an alarm that worked from the door switches etc.

rossnunn · Post by **rossnunn** » 02 Jan 2004, 19:03

Are any other electrics going a bit mad?? I had this on my Xantia when I first got it. Rubbish had clogged the drain in the scuttle panel so the water backed up and came in through the heater. Because of this there is a big multiplug under the passangers left corner of carpet (under a metal plate) this had corroded. making the electrics go mad - inc the alarm.
R

Robin · Post by **Robin** » 02 Jan 2004, 21:33

OK Fellas. Been through all those ideas, the floor is dry and clean so pulled the connectors and remade them. All looked bright and shiny new, found a pound coin under the seat too[:D]
Took all the door switches out, cleaned and remade all the connections and tested the system. It still went off after ten minutes this time.
Going into the Cit Spares centre for a solenoid for the idle circuit so will pick up a couple of ultrasonic door sensors and try those next.
This is wonderful site and thank you all for the ideas and support[^][^][^][:D]
Long live the Xantia.