R26 Alarm goes off after locking

Hi guys, riddle me this... so after locking the car, either using the door handle button, or the fob, the alarm goes off 30 seconds or so later. I had a quick search on the forum, and suggestions point towards a fault with one of the ultrasonic sensors. However, I’ve just tried unplugging each of them in turn, and then both of them together, but after each test, the alarm still goes off after locking.

If I open the car, hit the start/stop button 5 times and then get out and lock the car, the alarm does not go off. I thought this process disabled the ultrasonic sensors, but then surely unplugging them would have the same effect?

Any pointers, I’d be very grateful, as it is going to get annoying keep hanging around the car when locking it to make sure that the alarm isn’t going to start going off!

 

Just to update on this, for the price, I thought I might as well purchase a pair of interior sensors and see if that cures the problem. All fitted, no difference. The alarm goes off after 30 seconds of locking, unless I perform the ‘press the start button 5 times before locking the car’ routine.

So I’m a bit stumped now, and wondering if the disable function above also disables the bonnet sensor, or maybe the problem lies elsewhere. If no-one has got any suggestions, I will reach out to Cobra to see what they suggest.

On another note, changing the interior sensors was a faff. The cables must have been threaded through the holes in the C pillar trim before being soldered, as they were too small to pass the sensor plug through. Some careful Dremel action was required, which might be worth noting for anyone else tackling this job!

 

Just to update on this, the problem seems to have fixed itself the next time I drove the car. My next step was going to be to read the alarm flash code as I believe this tells you the source of the triggered alarm, but I can’t do this until the problem re-occurs.

Bonnet switch seems the most likely cause, but that would also mean that disabling the interior sensors also disabled the bonnet switch - might have to do some testing on that theory.


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