Battery for the factory alarm

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Battery for the factory alarm

Post by AlfaWhiz » Wed Jul 05, 2017 12:56 pm

Some good news here. I have successfully fixed my factory alarm siren by replacing the battery. If you had the tweeting birds noises coming out of your siren, then probably the internal battery was dying and you had to disable the siren.

What you need is a 7.2 V battery, original capacity was 280 mAh but I've used slightly bigger 320 mAh without issues. The battery is actually 6 x 1.2 volts, NICD or NIMH but it doesn't matter as long as it's rechargeable.

I've actually used this one here:

If you have problems sourcing one I can help, the one I've used was ca. 20 Euros.

Additionally, I had to swap out the alarm electronics as it was quite badly damaged by the leak from the old battery pack... Even copper in battery lead cables was badly corroded. I had a spare unit prepared for this.

I have also noticed that newer cars have an additional PCB soldered vertically to the main board. Not sure what it does, but the alarm works just fine when installed instead of the original one.

If you want to swap out the internals, I've found it the easiest, least invasive way is to remove the connector (remove all spades from inside the plastic end) and then push the cable with spades still attached through the hole where the cable goes through. To do this, just one spade connector fitting has to be removed from the cable. You can do it gently and then re-install the spade in place afterwards.

Some photos below. Enjoy! :D


More photos here: community/fotoboek/showalbum.php?upload ... eplacement

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alfa east
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Re: Battery for the factory alarm

Post by alfa east » Thu Jul 06, 2017 8:28 am

Nice and informative report. Thanks for posting!

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Re: Battery for the factory alarm

Post by pinino » Sun Jan 14, 2018 6:16 pm

It's worth pointing out that on the series I cars, the alarm battery can be simply deleted without disrupting the alarm and door locking functions (but alarm will not wail when main battery gets discharged). I quote "AndyM" from the AlfaBB:
On another note, with no batteries installed, the siren will work as intended for alarm, it just won't have the wailing feature when main car battery gets discharged. Meaning the batteries don't need to be installed to complete the remote locking and siren circuit. This could be looked at as a benefit, as you won't wake up the neighbors in the middle of the night if you haven't been driving your car regularly enough. Not a bad idea, in my opinion, to open the siren and de-solder batteries from the board if they look like they're starting to leak.

Here's the original post." onclick=";return false;

This may or may not apply to the TRW Sipea unit as well.

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Re: Battery for the factory alarm

Post by beeton » Sun Aug 12, 2018 12:16 pm

Do you have an image of the harness connector for the alarm and car side? The previous owner of my car patched some wires as they were broken at the harness and I think he may have mixed some up. Thanks,

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