How to Replace the Alarm Siren Module
 

I had a faulty alarm siren module that kept going off and here's how I replaced it:

Volvo Part Number 9499758. This is a complete alarm kit which costs less than just a replacement siren (??), but also provides some useful bits such as some good quality pop-rivets. Most of the remainder remains in the box, unused .

Firstly, you need to disconnect the battery.

Then, seeing as the siren is positioned inside the front wing in front of the OSF wheel, you need to partially remove the inner wheel-arch liner. Jack the car up, support on axle-stands and remove the wheel so that you can get in there to drill out the pop-rivets using a 6mm drill:

http://http://i869.photobucket.com/albums/a...oject002-1.jpg

You also need to undo 2 x nuts holding a metal plate. Then pull the arch-liner out of the way to reveal the siren:

http://http://i869.photobucket.com/albums/a...oject004-1.jpg

You have to remove the siren complete with its bracket which means undoing a security type bolt. I tapped the edge of it with a small hammer and chisel to free it, then managed to undo it with a small pair of mole grips:

http://http://i869.photobucket.com/albums/a...oject005-1.jpg

On removing the old unit, I undid the lead then connected it to the new unit and put it in place on the bracket provided. A new bolt is supplied with the kit with a torx head. Once you tighten the bolt, the torx head breaks off so that the bolt can't be undone again for security.

At this stage, I re-connected the battery, set the alarm and requested a cup of tea from Mrs Germanandswedish. In the meantime, the alarm didn't go off - good job; problem solved. Then having unlocked the car I put down a window and reset the alarm. After about 10 seconds, I put my arm into the car to check the interior movement sensors. All good - the alarm went off.

Then I proceeded to re-secure the wheel-arch liner using a good quality pop-rivet gun. I made sure there were no sharp edges left using a file, put the wheel back on and lowered the car.

Delighted to say that the alarm hasn't gone off since.