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Old 3rd October 2013, 12:17 AM
steamship's Avatar
steamship steamship is offline
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Join Date: Jun 2013
Location: Londonderry, Northern Ireland
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Default Replacing Your Broken Alarm Horn

Picked up a 2001 D2 FL a few months back and one of the niggles it had was it kept blowing one of the fuses, which also affected the interior lights. After some searching, the best possible cause was a failed alarm horn caused by leaking batteries. So I ventured, screwdriver in hand, to find the alarm and fix it. The following is how I went about it.

Remove the boot carpet by unscrewing the two plastic screws shown.



The alarm horn is located behind the trim on the left side of the car, behind the CD autochanger.



Remove the curved plastic trim at the side of the boot. There are two plastic lugs holding it in place. Pull the centre part of these out about halfway and then pull out both outer and inner parts.



This piece of trim is also secured by what I can only describe as industrial strength velcro. It is very tough indeed, so care is needed when removing it. If possible, try and ease the trim away from the car using a thin piece of wood between the trim and the car.



The next piece of trim to remove is along the back of the car. Here, you need to remove the two tie-down catches, two plastic lugs and the boot light. I think the two plastic lugs had covers (similar to others in the boot), but mine were missing. If you have them, just prise them off carefully, as they have a section that goes into the groove on the other lugs.



Now remove the boot light. Use a flathead screwdriver and gently prise it out from the end. Remove both wires.



Now remove the two tie-down catches using a Philips head screwdriver. Once removed, I tend to leave the screws in the catch for safekeeping.



It's now time to remove the trim itself. This was the one I had the most issues with, as I didn't know what else was holding it in place. Start to prise it off from the left side of the car, as the right side will still be held in place by the corresponding curved piece of trim. You may also need to prise it up ever so slightly, as mine was catching on the plastic base of the boot.



There are also four plastic clips holding the trim in place. Again, a thin piece of wood between plastic and metal for leverage is handy.



Time now to remove the CD autochanger. There are four 10mm bolts holding it in place. The one at the back right is the most awkward one to remove unless you have a knuckle joint in your socket set. Once these are removed, carefully move the unit out and back to get access to the cable. You are almost rotating it about the front right bolt.



To get better access, use needle nose pliers and squeeze the base of the plastic cable tie holding the cable in place. You should then be able to push it up out of the metal chassis. This will allow you to move the unit further into the boot area.



Final piece of trim to remove before getting to the trim is the access cover for the lights. A simple 90 degree turn and out it comes.



Strangely I didn't take a photo of the next stage, but what you now need to do is to gently pull the trim out from its position. You sort of have to take each piece of trim and draw them all together so that they don't catch on anything and then move it out and back, something like you do with the CD autochanger. The main thing is not to move it too far out as you may crease it.

If you now look up into the top recess, you will see a small black box secured by a bolt. This is the alarm horn, and the culprit. Simply undo the bolt, raise the alarm up and then pull it gently back towards you. Note that the cable is very short, so it isn't going to move far.



You should now be able to turn it around and unplug it from the loom. As you can see, the loom is very short indeed, and in my case even the plug has been corroded - so I can defintely say that the alarm is kaput.



And if you're interested, this is what the inside of the alarm looked like when I pulled it apart.



If you're lucky and the plug isn't corroded, you just need to get a replacement alarm. If it's like mine, then you either need to get a new plug (from where I don't know) as well. The alarm isn't specific to the A8, so others can be used, so long as they have the three pin plug. I was lucky to get one from a 05 A4, along with about a foot of the loom (BTW it's located in the lower right corner of the boot). Again, if you have to replace the plug, cut the cables as close to the plug as possible, as I took about ten minutes to splice the new one on. It was mostly done by feel.

The obvious next stage before putting it all back together is to test that everything works. Close the boot and lock the car with the windows open. Wait for it to arm itself and then stick your arms into the car. With luck, the indicators will flash and you will get an annoying; but comforting; noise from the back of the car. Mine doesn't beep when I lock or unlock it, but I might need to use VCDS to sort that out.

Reconstructing the boot is very simple. Just follow the same steps in reverse

Place the new alarm in position and secure in place with the bolt. Move the trim back into position, again being careful not to crease any of it. You may need to fiddle with it to get all of it to line up. Replace the plastic light trim cover. Move the CD autochanger back towards its original position when you first moved it out. This allows you to secure the plastic cable tie in the autochanger chassis. I marked the hole where it should go. This is more awkward to do than removing it. Once done, rotate the autochanger back into position, being careful not to trap any cables at the back of it. Again, a bit of jiggling about may be required to seat it properly. Secure all four screws in position first by hand before tightening them down.

The rear plastic trim now needs to be replaced. This is a fiddly bit, as you need to secure the right side into position with the curved right piece of trim. You also have to feed the two wires for the light through the relevant hole and then place the trim in position so that the four plastic clips are aligned to their respective holes. Holding the trim in place, start from the right side and push down on the trim above the plastic clips to secure them. You will feel them going into place.

The next part is fitting the light while you still have a hold of the wires. I'm not sure about the wiring, so wired it exactly as I took it off, brown cable at the bottom. Feed the light into place, cables first, and then push in to secure. Secure both tie-down catches and then replace the two plastic lugs. Replacing the curved plastic trim is done by aligning it into the slot with the bottom trim piece and then pressing it to the velcro. Use the palm of your hand over the four areas marked and apply pressure and you will feel it snap into place. Then take the two plastic lugs and place them in the relevant holes, and then push the centre part all the way in. You may need to jiggle the back one, as you have to align the trim and the plastic to the hole. Finally, replace the CD cover and then secure the boot carpet with the two plastic screws.

Addendum: Now that my alarm works, I wanted it to 'blip' when I locked the car. Came across a link to the following site 'Waks Wide Web', where it gives details on how to encode it with VCDS and a little downloadable program called BaseCode.

I hope you find this guide useful.
__________________
2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts

My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts

Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights

My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds

Last edited by steamship; 8th October 2013 at 03:04 PM.
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