Replace H12 Alarm Unit Backup Battery

[richard@thebrae]

Hi Has anyone replaced the backup Battery in a H12 siren unit located in the plenum chamber next to the battery of a 2001 Passat. I have searched the forums and google without any luck, plenty of folk with the need for this, but no experiance on the matter posted.
I cant believe that everyone is just sticking in a new siren unit (for the sake of a battery) at around £80 ago + fitting, if you cannot manage it yourself.
If you have please post the battery type and how to do it Please

[mrwlodek]

Hi,

I've got 998 VAG 167 backup siren in my Golf MK3. I will try reactivate this siren tomorrow. I looked inside. There is accu pack. New one is no problem. I have to check does the siren work. When I finish I share my experiences.

Regards
Marcin

[snapdragon]

There is a good write up somewhere with pics, will post a link if I find it.

[passat 130 tdi]

i put 2 new batteries in mine , it made no difference the alarm still only chirps like a sick bird when i lock all the doors. when activated the indicators flash but no sounds.This is an old thread now though , the guy ended up paying the full whack at the dealers.
Im going to argos for a 1 wire quick fit alarm with built in voltage dropper and shock sensor all for £29-99 , the vw immobilzer should still do its job when i lock the doors with vw fob.