I'm back, having just fixed my ICV. I've now got another issue - the car alarm.

I've noticed this a few times before - that is, whenever I've had to disconnect the battery, the alarm goes potty for the next few days. The last time I did this (to change the alternator) the alarm would sound for no reason. At the time I suspected the bonnet switch/sensor. Eventually, the alarm stopped going off for no reason and all was well. Today I fixed my ICV, and now it's happening again. Except this time it's much worse. Now the alarm 'pips', even when the car is unlocked and the alarm is deactivated!

If I leave the car unlocked, after about 5 to 10 minutes it starts 'pipping'. By pipping I mean the alarm horn sounds very very briefly, about 4 times a second, for about 2 seconds. Like a rapid series of gentle taps on the horn. The indicator lights flash too, so I know this isn't a 'car horn' problem, but an alarm problem.

I took the car out for a 20 mile 'warm up', and reset my audio lock and re-programmed the electric windows, as you're meant to do, and on the road the car was fine. But as soon as I got back this happened:
[list]
[*]I locked the car up and waited
[*]within a minute the alarm sounded
[*]I used the keyfob to unlock the car
[*]the alarm stopped sounding, but the pipping thing started up almost immediately
[*]I got in and started the engine - the pipping continued
[*]I drove the car a few hundred yards - the pipping got worse
[*]I stopped the engine and got out - the pipping stopped.
[*]My car now sits with the battery disconnected again
[/list]
I see only a few options (for someone with too little cash to have an engineer look at it) :
[list=1]
[*]Disconnect the car alarm so that it can't do this
[*]Disconnect the horn, so the alarm can't sound (only flash)
[*]Disconnet the battery each time I park up (can you imagine that in Tescos carpark?)
[*]Set fire to the car
[/list]
Anyone have any advice please? Would the alarm system be easy to disconnect? Would that even work?
I think the alarm's horn is different to the 'in car' horn, so could I just find the alarm's horn and unplug it? I know the lights would still flash, but if it righted itself in a few days then I'm sure the neighbours wouldn't care about a few nights of occasionally flashing lights

Take the car to an auto electrician. They can diagnose the problem using multimeters and diagnostic tools.

[quote name='H3lly' post='44524' date='Sep 27 2009, 11:34 AM']Take the car to an auto electrician. They can diagnose the problem using multimeters and diagnostic tools.[/quote]
Thanks for the advise but I simply can't afford that. No matter how cheap

I've tracked (through the sound of the alarm) the noise down to somewhere over the left rear wheel arch. So I've stripped out the boot trim right back to the metalwork. I can see plenty of wires, but no 'brains' or horn anywhere. So I've jacked her up, removed the wheel and the dirt guard, but there's nothing up inside there but solid metal. Somewhere between these outside and inside skins is the horn - but it all seems to be welded up! I wonder if it's not possible to get to it?

I only want to disconnect the horn so that it can't make any noise in the middle of the night if it decides to randomly go off

Has anyone got information on the wire colours for the alarm - if the wires I've found go to the horn I could cut them!?

Well, after a long time searching and cursing, I found the alarm horn - and boy do I feel stupid! It should have been so easy to find, I can't believe it took me so long! Anyways, I've disconnected that, so now I have a faulty alarm that can't make any noise. One step better at least.

Then I started test door sensors etc, to try to find the faulty one (I'm presuming there's a faulty sensor). Eventually, my suspicions fall to the bonnet catch. This thing seems tetchy. So I disconnect the plug and short it with a piece of wire. This time, after arming the alarm and waiting - nothing happens. So in the end I've left the plug shorted out and cable-tied up out of the way. This does mean my bonnet is unprotected, but no thief is going to try the bonnet first are they?

So far so good. The alarm has been armed for 5 hours and it hasn't gone off. Yet. If it stays ok for a few days, I'll reconnect the alarm horn. That way my alarm will be 90% functional, which is better than off!

(I found out from somewhere that if you press a door light sensor six times in eight seconds, it puts the alarm system into a door check mode. Not sure about how you're supposed to use that to your advantage, but someone might find that snippet of info useful if they read this post in the future and want to test a door or boot sensor)

Cheers everyone.

[quote name='Thoric' post='44616' date='Sep 27 2009, 09:03 PM']Well, after a long time searching and cursing, I found the alarm horn - and boy do I feel stupid! It should have been so easy to find, I can't believe it took me so long! Anyways, I've disconnected that, so now I have a faulty alarm that can't make any noise. One step better at least.

Then I started test door sensors etc, to try to find the faulty one (I'm presuming there's a faulty sensor). Eventually, my suspicions fall to the bonnet catch. This thing seems tetchy. So I disconnect the plug and short it with a piece of wire. This time, after arming the alarm and waiting - nothing happens. So in the end I've left the plug shorted out and cable-tied up out of the way. This does mean my bonnet is unprotected, but no thief is going to try the bonnet first are they?

So far so good. The alarm has been armed for 5 hours and it hasn't gone off. Yet. If it stays ok for a few days, I'll reconnect the alarm horn. That way my alarm will be 90% functional, which is better than off!

(I found out from somewhere that if you press a door light sensor six times in eight seconds, it puts the alarm system into a door check mode. Not sure about how you're supposed to use that to your advantage, but someone might find that snippet of info useful if they read this post in the future and want to test a door or boot sensor)

Cheers everyone.[/quote]

Ford bonnet switches are notoriously iffy. If it does prove to be this all you need to do is get a new courtesy switch from somewhere like Maplin (costs pence) and wire this into the wiring for the current switch. You could then extend the wires and position the new switch somewhere that water wont get in it as easily and you'll have a 100% working alarm.

where did you find the alarm horn???? dont really want to take the whole car apart to find it

Rear of the boot on the passenger side i believe open the boot and you see the carpet cover should be behind that on the wheel arch

Always thought/assumed it was the same horn. Might be useful to know in the future!

That should be the control box on older fords it was linked to the car horn that was the sounder im assuming its the same set up