Alarm going off!

[petergl1800]

My alarm keeps going off for what appears no reason?
The only thing which appears the same is that it was raining quite hard.
Does anyone know what could cause the alarm to go off?

Thanks.

[PaulGover]

It's your dog wagging his tail

More seriously, unexpected alarms can caused by vibration and air movement. We live next to a vets, and when their customers leave their second pooch on the back seat, their bounding around usually sets the alarm off. Another big issue in warm weather is leaving the window open a little; the air currents can confuse the ultrasonic intrusion detector and trigger an alarm. If that's the cause, the nearest thing to a solution is to get one of those cardboard sunshades behind the windscreen to keep the heat down, and leave the windows shut. There's a "disable vibration and ultrasound" setting somewhere for use on ferries and the like. You perform some unnatural act such as holding the handbrake button down while opening the door to select it. It's not that, and I forget what it is, and using it of course lowers the protection offered.

Of course, it could just be something not working right.

[BrianG]

Apart from the causes that Paul has mentioned a perennial favourite for false alarms on the X350 is the bonnet switch not functioning correctly. This can cause the alarm to go off randomly for no apparent reason, sometimes several hours after leaving the vehicle all tucked up for the night. The switch itself can be faulty or the connections to it can be corroded; as it's a 'normally closed' circuit any cause of high resistance will set the alarm off. If you've been oiling the bonnet catches and cable release (to avoid the common 'broken cable' problem) this can also get into the switch and upset it - always use grease here!

[petergl1800]

Many thanks Brian, I will have a look in this area.
Kind regards

[robv12]

agreed, bonnet switch, constant problems, here, just by pass it

[petergl1800]

Thanks to all.
Only problem is that I have had a good look and I do not have a bonnet switch!
Please advise on any other ideas.
Many thanks

[BrianG]

Thanks to all.
Only problem is that I have had a good look and I do not have a bonnet switch!
Please advise on any other ideas.
Many thanks

Peter, unless someone has already disabled it, yes you do! The workshop manual shows it's fitted to the right hand latch assembly (viewed from the front of the car) so I think you'll have to remove it to gain access to the switch. That's an assumption as I did not have to do mine in the end *. To check if your switch is present and working just leave the bonnet up and turn the ignition on (make sure you shut the driver's door or this message takes precedence). You should see "Bonnet Open" on the message display. If you don't see the message then it's probably been disabled and there may be another cause for the alarm going off.

* One tip regarding an erratic switch: if you normally tend to 'slam' the bonnet to close it the switch sometimes does not make properly. Close the bonnet until it's resting on the safety catch then, placing a hand over the latch position on either side, then press down smartly together. This solved the apparent problem with my switch; it also makes sure that the thin aluminium bonnet sits properly against both rubber stops.

[PPV]

Do these cars have boot switches also? One of mine did and that caused the problem.
Regards,

[BrianG]

Do these cars have boot switches also? One of mine did and that caused the problem.
Regards,

Yes they do have boot (trunk) switches and can also cause the problem. However, in the case of the boot 'switch' it's part of the lid locking motor mechanism; it's actually a pair of changeover switches that have to work in a particular sequence, so not a separate switch as such.

If you have trouble with the either the 'switch', or the failure of the motor locking lid system to work reliably every time you try and close it, then it's worth changing the cheaper link cable assembly before the expensive lock assembly (ask me how I know!). The link cable (official part name is 'trunk harness link lead', e.g. part no. C2C21435) is the short, ribbed rubber-covered cable loom that loops from the top right corner of the boot into the bodywork; it carries all the interlock switch circuits, and power for the lock motor and number plate light. Although it's better than the earlier designs such as the X300/X308 it can still suffer from one or more broken wires after 10 or more years of use. It's easy to change as (unlike the X308) it just unplugs at both ends, but check your VIN as the part number for some earlier cars are no longer available; if you're one of these then you'd have to trace and repair the broken wire(s) instead just like X300/X308 owners.

[snaefell]

Looks like I may have this problem, I say that because my alarm keeps going off & I keep getting the message 'bonnet open'-bit of a heavy clue!
Just how easy is it to sort when you haven't got a clue what you are looking for (or at!),& I am having trouble getting hold of a workshop manual?

[BrianG]

...... I am having trouble getting hold of a workshop manual?

You wont find a hard copy workshop manual. The choices are to download a copy from a site such as jagdocs.com or pay for a subscription (daily, weekly, monthly, or even yearly) to Jaguar themselves at TOPix.com. I paid $10 for a download copy and a whole load of service bulletins together with the electrical wiring diagrams download - much the most useful document. There really is not a good picture of the bonnet switch in the workshop manual: this just shows the general area of location. The best plan is to undo the clips and remove the top cover (the black piece of plastic that goes right across the front above the radiator) and have a look at the nearside bonnet catch area and explore from there! To get at the switch you may have to remove the front grille (just pops inwards if you press firmly)

[snaefell]

Cheers Brian,looks like I have managed to get a manual download to give me a clue,it's going to have to wait until tomorrow now,it's suddenly gone very dark & started to throw it down again!!