C5 Alarm keeps going off after battery disconnection

[BillJonez]

I got an RAC technician to check my cars fuses and battery as the windscreen washers weren't working.. After he left the car's alarm went crazy and goes off randomly if I lock the car using the fob. The fob then doesn't work and I need to open the car manually with the key and switch on the engine to stop the siren. The clock also resets Everytime this happens. Took the car to a Citroen dealer and after paying £85 for diagnostics they told me the only fault they could detect is a low siren battery and they would suggest changing it for £250 and this "might " fix the problem! Anyone had a similar problem? And does this make sense??
N.B I've tried the battery reset procedure several times with no success
Thanks

[Sloppysod]

Welcome, there are some wise people on this forum, who between them will be able to help answer 90% of teh questions asked lets hope this one is not in that 10%
But
I don't know, but have to re-initialised the remote control after the battery was disconnected, it may help?
These are the instruction how from the X7 owners manual.
"Re-initialisation of the remote control
After a change of battery, it is necessary to re-initialise the remote control. To do that, switch on the ignition and immediately press button C (The lock button) of your remote control until you achieve the desired result. This may take some ten seconds."

[GiveMeABreak]

Hi and welcome to the Forum.
A couple of things first you can try. Every now and then the car keys lose synchronisation with the car. Put the key in and turn the ignition on and hold the lock button down for about 10 seconds to re-synch. I assume your fob batteries have a good charge? I say this because the car is armed using the fob. It is normal that once locked with the fob, then opened using the key it will set the alarm off, until you put the key into the ignition to turn it off.

Until you resolve the issue you can always lock the car with the key only - don't use the remote on the fob. When locking with the key only, this will not activate the alarm.
If there is a Siren issue, with the key in the ignition,and switched on, the ALARM button (the middle button on the bank of three on the right of the dash) will light up for 10 seconds.

So there could be 2 unrelated issues here which may give the impression that more is wrong than there actually is: the key fob battery or out of synch, resulting in having to unlock the car with the key, resulting the activation of the alarm...

Check around the battery area and make sure the connections are tight. If Citroen have not found any other fault that is encouraging. Assuming you have no other issues and you lock and unlock the car with the key temporarily, it may well be the siren battery. These systems are designed to go off if any of the circuits are tampered with or disabled - so if the siren battery is end of life and it is not recharging properly, it may think that the power has been cut and will activate.

[Richard_C]

Can't help with Citroen but it was a common problem with the SAAB 9-5 I used to own. Alarm is designed to sound even if battery is disconnected and as others have said that battery can get tired and fail. Happened to me and I bought the new box (in a rush about to go away so no time to try other ways. Cost was about 250 back then. The SAAB forums came up with 2 workarounds. One was to open the box (needed brute force and hot metal to cut away a bit of plastic), split battery pack open, identify the rare rechargeable cells within the battery, order them from rapid electronics, fit, seal and refit. The other was to access the box, cut wires to sounder, and live without an alarm. I don't think you could just disconnect and throw the box away, the ECU wouldn't let you start the engine. This all from memory - it was 7 years ago.

Hopefully a key reinitialise or a check on all connections (don't forget the earth side) will solve it for you. If not, the alarm box might be the problem.

[Bigwez1]

Hi did you solve this my c4 grand picasso is doing the same thing

[GiveMeABreak]

There are a couple of different issues in this thread, please describe what your particular issue is with as much detail as possible.

If your alarm is randomly going off after locking the vehicle at various times, it can be several issues, such as a faulty bonnet alarm trigger, or the alarm siren module that has failed.

I recently replaced both in the C3 to cure the problem.

[Bigwez1]

Ok when I use the fob to lock the car as soon as it hits the 3 minute when the bsi powers off the alarm goes off, the fob won't work to open the car, I have to open the car by the key and turn on the ignition to turn off the alarm, if i dont arm the alarm fob still dosnt work after the 3 minutes, central locking won't work etc until ignition is switched on, clock always rests when bsi powers off as will, I have reset the bsi a few times but nothing has changed, thanks in advance

[GiveMeABreak]

Ok, so there is a little more going on here than just the alarm it seems.

The next step would be a diagnostic to see what is happening, but you may need to try and reinitialise the fobs.

To reinitialise the key, place the key with the fob buttons facing you into the ignition, turn ignition on and within 10 seconds, hold the LOCK button down continuously for at least 5 seconds.
Remove key, close vehicle and then operate the remote which should now operate the central locking. Ditto for the second fob if you have a second fob.

Also check the batteries are healthy in the Fob.

[Bigwez1]

It's still the same, think it's looking like I will have to get it plugged in some where to find the fault, thanks for your help

[wheeler]

Do you have an aftermarket radio (or any other aftermarket electrical equipment) fitted?

[Bigwez1]

Radio is standard, it dose have after market front parking sensors that don't work, I unplugged the fuse for them

[GiveMeABreak]

I assume you mean an independent in-line fuse for the parking sensor kit? As long as this wasn't a standard fuse in one of the car's fuse boxes! Each fuse serves multiple equipment fitted to the car, so removing a standard fuse may have consequences....

[Bigwez1]

Yes, all the wiring is a bit untidy for it, might completely disconnect it all at weekend when I get time

[Mark Clayton]

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!

[Bigwez1]

I'm just living with this problem 1 year on, I just lock the car by the key, but I'm going to have a look at them shunts in the fuse box and try moving them