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Author Topic: Alarm sometimes goes off when I turn the key.  (Read 1504 times)

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Grrrrrr

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Alarm sometimes goes off when I turn the key.
« on: 23 October 2009, 10:16:45 »

Hi all,

Erratic problem with the alarm on my facelift (2001) CDX alarm. Sometimes when I turn the key to start it the alarm sounds. Doesn't stop me driving off but it sounds for about 30 seconds giving me some odd looks from some shoppers!

Is this something common or am I reduced to waiting till it becomes consistent and then trying to trace it? Any ideas where to start tracing from?

Cheers.

J
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Dave DND

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Re: Alarm sometimes goes off when I turn the key.
« Reply #1 on: 23 October 2009, 10:25:00 »

Quote
Hi all,

Erratic problem with the alarm on my facelift (2001) CDX alarm. Sometimes when I turn the key to start it the alarm sounds. Doesn't stop me driving off but it sounds for about 30 seconds giving me some odd looks from some shoppers!

Is this something common or am I reduced to waiting till it becomes consistent and then trying to trace it? Any ideas where to start tracing from?

Cheers.

J

Usually a sign that there is a low battery voltage being detected, and that cranking the car is dipping the voltage below the acceptable threshold set by the alarm.

Even if the car starts ok, its still worth checking out the battery and charging circuits and earth connections before the cold weather hits, and if all that fails, then replace the batteries in the power sounder as a belt and braces fix.

 :y
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TheBoy

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Re: Alarm sometimes goes off when I turn the key.
« Reply #2 on: 23 October 2009, 16:33:13 »

Suspect its the power sounder failing.  Bet the alarm noise is electronic siren rather than horn noise?

I see you're in Bucks, if its the north end of Bucks, I'll happily show you how to remove it.
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feeutfo

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Re: Alarm sometimes goes off when I turn the key.
« Reply #3 on: 24 October 2009, 03:10:12 »

i had this, changed the car battery, and it stopped the alarm going off, you may find the Alarm goes off on Monday morning if the car has stood all weekend allowing the voltage to drop further.

Theory then is cranking the starter draws all the remaining volts which may already be low, the power sounder sees the voltage drop below limits and thinks a thief is disconnecting the car battery.
The power sounder then goes off independently with its own power source, which is there as a back up if the car battery is disconnected... or flat i suppose. If the car alarm is genuinely tripped under normal conditions you should get the horn alarm as opposed to the siren of the power sounder.

It is also possible the power sounder is playing up,  i cut mine open to have a look at its internal batterys which had leaked very slightly but had not affected the circuit board. Pics of which can be seen in maintenance. Would recommend you do the same and have a look, if they leak they can bugger the circuit board and it may start going off at any time, even while your driving. For info, if you hear 4 pips from it they say the sounder is telling you its batterys are low. Never herd that with mine. And with a good circuit board and no pips I was happy the car battery  was passed its best.

Oh yes, should add my lpg software has a battery voltage indicator included, this showed the battery to be low. Strangely Kevins tech 2 showed a slightly higher voltage but still a fraction low, and considering i had just driven the car for an hour and only been stood for a further hour when Kevin looked at it, all added to the case for a new battery.

Hth

Ps. see Kevins step by step guide for checking your battery, if you have a meter, or slightly easier, get The Boy to have a look, you wont find better. :-)

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Grrrrrr

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Re: Alarm sometimes goes off when I turn the key.
« Reply #4 on: 30 October 2009, 13:14:39 »

Cheers chaps. I'll have a nosey at the maintenance part of the site then get the bonnet up and have a poke around.

I'm mid-Bucks (Aylesbury) rather than North Bucks (Milton Keynes) but not far for me to travel. Not working today so fiddle time!

Will check the voltage across the battery. That should give me an idea of how robust it is. As long as it is over 13V I'll assume it has some life left in it!
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Grrrrrr

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Re: Alarm sometimes goes off when I turn the key.
« Reply #5 on: 30 October 2009, 13:15:41 »

Oh, you were quite right. It is the electronic siren rather than the horn. That said, it hasn't done it this week yet.
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Grrrrrr

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Re: Alarm sometimes goes off when I turn the key.
« Reply #6 on: 30 October 2009, 16:46:21 »

Looks like the power sounder is held by 2 bolts to the air intake quite low down. Can see why they'd need a good seal down there but to completely encase it? Nuts. Trying to think of a nice method of getting inside that can easily be resealed and doesn't involve a hack-saw.
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Boracic

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Re: Alarm sometimes goes off when I turn the key.
« Reply #7 on: 31 October 2009, 11:37:12 »

The power sounder is under the scuttle cover, its a 10 minute job removing it, I took mine out as it started going off like your when I started the engine, then it got worse and just went off for no reason
http://www.omegaowners.com/forum/YaBB.pl?num=1220198611
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Grrrrrr

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Re: Alarm sometimes goes off when I turn the key.
« Reply #8 on: 31 October 2009, 17:02:55 »

Ah, must have been looking at something else, although the wires seem to end up under there somewhere ... after a tour of the engine bay.

Checked the battery first thing this morning after a day's rest. Only 12V. So, battery past its best, although not that bad. However, with winter approaching it might make sense to replace it anyway.

Mine's a 51 plate so reckon it is probably worth pulling the power sounder apart too. Thanks for the link. Cannot seem to find a Haynes manual for this model anywhere so lost without this site.
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