I had some time to kill so thought i would replace the backup batteries on the OE siren,As you know the Bosch piece of junk isn't designed to be opened as it is ultrasonic sealed, Take out the Siren as in the Remove power sounder how to. Your going to need a dremel or similar cutter
Two Varta Ni-MH 3/V150H, 3.6v batteries @ 140mAH, try ebay for the batteries
LED legs 8 in total, some gloves, A soldering Iron and solder
Amalgamating Tape, Some primer
and some sealer
Cut round the seal of the siren with the dremel
Now it's in two half's separate the two half's taking care not to bend the pins on the back and then unplug the module from the siren and then release the module that is held in by four plastic clips
As you can see the siren battery has gone
My battery didn't come with any pins
as it would of been a pain to bend or move pins fitted to the battery as their is no direct fit battery for the siren.
So i tinned the ends of both batteries taking not to heat them up too much, i did one side and the went to the next battery to allow it to cool down before doing the other side
Remove the batteries i just clipped the terminals as i couldn't find my desoldering tool,you can see where the acid has started to burn the board
Take care when soldering the pins and batteries to the board as the cooper on the board is starting to get exposed and could short out the batteries if the pins conduct on the copper
The batteries are really close and with the solder on the battery it could touch so i used amalgamating tape only on one of the batteries as that was all that was needed
with both batteries fitted you are nearly ready to rock n roll
Make sure the pins bottoms are soldered properly after you soldered it onto the battery,just apply some heat and some solder to the bottom of the pins And make sure the solder has not bridged a circuit on the chip part of the board
Clip the circuit board back and replug the siren
Now just put the two half's together
just to test it on the car, Mine chirped when i fitted it, arm the alarm with the window down and give it 40 seconds to arm, set it off by waving your hand inside the car the siren and the horn should sound then press the disarm button,now unplug the siren it should sound in an audible alarm,plug it back in and turn on the ignition now you can remove it from the car.
Prime both half's of the siren Make sure the excess primer is removed
Make sure you seal it with something strong i'm using windscreen bond don't skimp on the sealer
allow 24 hours to dry and then refit to the car and test. HTH
The Author takes no responsibility for damage caused to vehicle as a result of following this guide.