C8 Alarm Goes Off For No Reason

[rfhspares]

If I lock the car using the key fob,most of the time the alarm will go off for no reason, sometimes within minutes and sometimes after hours, sometimes not at all but being woke up at 2am by the alarm is annoying. all doors are tightly shut and I tried covering the sensors inside the car just to make sure its not them. still does it though. My thoughts are something is draining power and the alarm system is spotting the power drain. Any ideas? Edited March 17, 2015 by rfhspares

[paul.h]

Maybe one of the sensors/switches is giving a poor contact. There will probably also be one under the bonnet to check. Do you have any messages on the dash that indicate when a door is open and if so are they showing the doors are closed when using the car that might suggest a poor contact ?

[rfhspares]

There is a dash board display and it does show all doors closed and works as it should. When the doors and boot aren't shut properly the doors won't lock. Can't see a switch anywhere for the bonnet but I will have another look.

[paul.h]

To check if there is a bonnet switch, leave it open and see if the alarm goes off. On our C5 the bonnet switch is near the front to one side. When the battery in our C5 goes flat it does not set off the alarm so I suspect a battery drain would not be the problem.

[rfhspares]

Cant see a bonnet switch anywhere. Left it unlatched and lifted the bonnet while alarm was armed but it didn't set it off so think it rules out the bonnet switch.

[rfhspares]

Alarm hasn't gone off at all for the last week. Only thing I have done is clean all the electrical contacts with emery cloth on both sliding doors and I sprayed switch cleaner in to the ultra sonic sensors next to the interior mirrors just to clean them of a bit. Not sure what problem was but must have been one of these 2. Edited March 24, 2015 by rfhspares

[paul.h]

It is always good when a fix only costs a bit of time.

[Richiejh]

I had a similar issue, Lexia listed the interior sensors as the trigger so I turned their sensitivity down to minimum on lexia which stopped it instantly. An easy test is to use the switch on the end of the dash to disable the sensors and see if the alarm still goes off.