C5 Alarm keeps going off after battery disconnection

[white exec]

Two thoughts...
- Does the car have volumetric (cabin) movement detection? This can misbehave, or be affected by thermal air movement. Can be switched off on some models.
- Is there a proper alarm reset procedure, after battery disconnection?

[GiveMeABreak]

1) Yes - Perimetric and Volumetric as standard.
2) No, just the standard Battery Connect / Reconnect Procedure.

[white exec]

Worth trying switching the volumetric off, as a test?

[Hell Razor5543]

I recall, in the past, having to replace the 'microphone' ultrasonic sensor on my Xantia, as it was not working properly and causing the alarm to go off for no good reason. The new 'microphone' sorted this out. I also recall that Mandrake (Simon) had a similar issue with one of his Xantias, and he was able to replace the microphone and fix the problem. While I am aware that the OP has a C5, it may be possible it has developed a similar fault.

[GiveMeABreak]

That's why Chris already suggested deactivating the volumetric (there is a button specifically for this) to test it.

[Bigwez1]

Hi. The RAC man simply put the SHUNT fuse ( in the glove box site) ¼" to the left and as a result the car was in dealership mode. If the fuse were moved to the right, all would be back to normal. No dealership extortionate charges!

I moved the shunt today and it's worked, can't believe it's something so simple after all this time, thank you

[Viko]

Gentelemen, i had the same isssue for 3 year. i could lock my C5 only with a key because each time if i will lock with remote control it will go off after 3-5mins. it was impossible to is use it at all. I when to check SHUNT fuse i move to right side and final all is OK. I would like thank you all of you. Stay save and healthy.

Regards
V

[GiveMeABreak]

@ Viko: You'll probably find you need a new alarm module - Once the independent internal battery fails, it's the same as if somebody tried to cut the supply - it triggers the alarm. Although they last a long time, once they fail they will constantly go off as they cannot hold a charge for very long.

I had the same issue on the C3. Locking with the key does not arm the alarm - only with the remote. I replaced the alarm module (a simple job) and everything is fine.