My original post ….

https://www.brickboard.com/AWD/volvo/1648416/V70-XC70/alarm_system_service_required.html

….is getting pretty old so I decided to repost with details as to the fix to my dead alarm battery and the resultant “Alarm System Service Required” indication I was experiencing. It may just help someone else who finds themselves in the same boat. Klaus had asked for details so here goes. Sorry it got so long.

Thanks to several YouTube videos and Volvo forum posts I was pretty sure what I was going to find inside the siren module. So before I even started the project I had Batteries+ build a (6) x 1.2v AA 1100 mAh NiCad battery pack (=7.2v) with pigtail leads. They charged me $25 total for the batteries and the labor to build the pack. I was pretty sure the new battery pack wouldn’t fit inside the siren box so I made plans to relocate it to the ECM/TCM box. This would also make future battery replacements MUCH easier. Besides, I don’t know how long the AA batteries will last compared to the OE batteries.



I fashioned a box out of some thin gauge galvanized tin with some foam padding inside to cushion the battery pack. The ends of the box can be bent open and closed to access the battery. Through blind luck I made the box 7/8” wide which allowed the bottom of it to fit snuggly into the unused slot in the bottom of the ECM box. A single pop rivet secures the top of it to the ECM box.





The siren module is buried inside the front RH inner fender, behind the RH headlight assy. Plenty of YouTube info on the removal process. I chose to disconnect the car’s main battery at this point. I don’t know if it was really necessary or not. Once extracted, I used a small hacksaw to separate the two halves of the plastic siren module. You want to be careful to not cut any deeper than absolutely necessary to separate the two halves. As I feared, the original 3-stack battery pack had been leaking and probably for some time.





The positive wire, where it plugged into the circuit board, was toast to the point that I couldn’t re-use the original plug. At that point my car was torn apart so I couldn’t drive somewhere to get a proper plug. I found an old cordless phone battery pack that had a plug that fit “quite well” after I carefully filed a couple nubs off of the sides. It fit good and snug. I’m still a bit concerned about the connection as the + pin in the circuit board was a bit corroded. A really good fix would have been to replace the socket on the circuit board and use a properly matched male connector on the leads. Oh well, it is what it is.

I drilled a hole in the siren box through which to run the battery leads and used a grommet to protect them from chafing. This hole can’t be drilled where it interferes with the mounting bracket. I also protected the wires with a continuous piece of shrink tubing that runs all the way from inside the siren box to inside the ECM box, with a grommet also where it enters the ECM box. It’s about an 18” run, going through an opening behind the headlight. I didn’t actually shrink the tubing as it would have made it more difficult to route. I know I’m really anal about wire protection but that’s the way I am.

A couple bullet connectors inside the ECM box connected the leads to the pigtails on the battery pack.



So far I’ve done several engine starts and one overnight rest without an “Alarm System Service Required” indication. Fingers are still crossed.