XC70 siren back-up battery
 

Hi everyone,
Getting message saying ‘ alarm system malfunction service required’
I believe this is a common problem and is caused by failure of the rechargeable
back-up batteries in the siren. Main dealer said the rechargeable batteries are not
replaceable and a new unit is required at around £120 plus labour!!! This seems crazy to me and what an awful design. Searching on-line/YouTube shows people changing the battery pack but it’s difficult to get to. Dealer also said back-up battery is charged from a feed from the main battery not the alternator. Anyone have any views, ideas, experience of this issue? New battery just fitted by the way.

What age car?

On the P2, the alarm can be accessed from under the OSF wheel arch, there's a security screw to deal with then it just unplugs and it's out.

To access the battery you need to cut the unit open as it's sealed, then it's a simplish case of taking the old battery out and soldering a new one in.

Then reseal the alarm unit and refit.

This, providing the battery hasn't leaked.

XC70 2014

There’s some stuff on YouTube about accessing
via the wheel arch which involves drilling out
loads of rivets. Don’t fancy that.

Why? Drilling out rivets and popping new ones in is easy.

I refitted the wheel arch with push in plastic trim rivets, easy

Removing the alarm siren from the wheelarch is quite straightforward, replacing the internal batteries is a bit fiddle but easy enough, although you'll need a soldering iron, batteries are readily available on ebay and there are plenty of videos online to show how it's done...

If the dealer can replace the siren for £120, that seems quite a good price, usually nearer the £150 - 200 mark...

https://www.ebay.co.uk/itm/Volo-Alar...MAAMXQpwFRaZur

https://www.ebay.co.uk/itm/Genuine-V...hash=item2f0da

Why not buy a new unit and fit yourself