How to modify Volvo Alarm Siren after it has given Message: Alarm system Service Required Ver. 1.2 We will show how to modify the Alarm Siren Unit without using Battery. If you are not sure or do not know anything about Electronic, DON T do this! Also Remember by doing this way your Alarm will not sound if someone disconnect the cable as you do not have any BATTERY in the unit which normally make the sound if the 12V power is broken. First take out the Alarm Siren Unit, there are a lot of information how to do that on internet. Then split the unit in two by using a saw, but be careful so you do not saw to deep and damage the pc board inside. Ideal is ca. 8mm down from the black part of the unit. 8mm from the black part is the ideal place. Picture shows after we modified and glued the parts together again.
If you take a 12V DC power supply and your PC board is not too damage you can easily charge your battery up to 5 to 6V just for testing the unit so you do not go and buy battery in vane if you choose to replace the battery. Charging will take from 5 to 8 hours and testing can be done by taking the cable out in front of the wheel and just connect the unit for testing. We did this and found it was not working even with Charged Battery, so it had to be some more which was damage. After checking diodes, transistors and signals to some components we discovered the Siren itself did not work, and also one cable was lose. We opened the Siren module and found that one cable had loosened. If it is OK you should have some ohm when you measure the siren, but it will not be constant, it will be going from 0 to 4 to 12 ohm. If it shows nothing it is broken. 10 plastic pins have to be drilled by an 8mm drill to separate the unit. To take out the Siren module you have to use an 8mm drill to drill all 10 plastic pins which hold the Siren Module together. You have to use a screw driver to bend the two parts apart, but be careful.
One cable was lose and we solder it back again in a new place. Old place, but the metal was damage. There is an O-ring which are important so be careful. Then we put it together with a rubber between the pc board. This rubber when you put back the PC Board will press the plastic part over the Siren Unit. Then we did one more time testing with our old Battery which we had charged and it worked. But as if we replaced the old Battery with new ones we would have the same problem some years from now so we decided to skip this function and make some modification to get the unit to operate without battery.
Instead we used 100K resistor in series with +12V which are on Pin 1 in the connector and we used a Zener Diode 6,2V (you can also use 7,5V) and a diode 1N4148 to be sure we do not get any power the wrong way. IC for Commun ication GND CPU unit +12V Pin 1 connector R1 100K D1 1N4148 Old + (7,2V) from Internal Battery D2 DIODE_ZENER 6,2V You can also use a 7,5V Zener Diode Old GND (-) from Internal Battery
D2 is to be sure the other 2 small IC s on the PC Board does not get more power than max 7V, in this case the power will be around 6,4V as the car battery will give 13,46V normally. D1 is for protection backwards as the Alarm Unit Battery may be charging from the car battery; we are not sure of this, but this way it will not be any problem with that. The 1N4148 can be changed to any diode. After we put some special glue for plastic all around and put everything together again.
We also used the Rubber under the PC Board to be sure the plastic would be pressed together even we used glue to be sure the Siren would work as it should. After we glued the whole unit together and used some electric tape to hold it waiting for the glue to dry. We also put some extra glue around outside the unit to be sure it will not be any problem with water inside the unit. In the end we put 2 plastic Strap around to be sure it would not fall apart. And we used Nail Polish on the PC Board where it was damage as protection. We hope this would help someone which have problem with the Alarm Unit on a Volvo and if you need some more Tip and Trick you can always look at our web site, www.nasab.com/volvo And if you need some help you can always contact us at smed@nasab.com and we will see if we can help you. There is also a lot of info on Internet which says you have to set some counter and the battery is only for counting down some sequence and a lot of other wrong info, all of this is wrong, when the battery goes under a specific level there is a IC which do then send a signal to the CPU IC on the PC board which then gives this message Alarm system Service Required. You do not have to go to Volvo and reset or set any counter in VIDA, if you get some problem you just disconnect the GND on the battery in the car, wait for some minute, set the key in pos II and connect the battery GND back again, then the car will reset itself, read all the data and the Alarm will work as normal again. We can also mention if you have got a message saying System Engine Service Required or your Motor sign lightning or your Cruise has started to not show up when you push the button it also has to do with Alarm Siren does not work and it will disappear when you get this to work. We had this
fault for 2 years coming and going, our Mechanical workshop could never get what was wrong but after we fixed the Alarm Unit all our Error was gone and has not been coming back. This of course as long as you do not have something else which are wrong which can also create this message. Some extra info: IC-4269G, 5-V Low Drop Fixed Voltage Regulator. Sensing internal battery level and if the level goes under a specific value it will send info to CPU and you get an Error Message. Alarm system Service Required MosFet 3055VL GND Communication IC-L9637D for communication +12 V Battery CPU LSC 441309CFN Unit
The Alarm Unit before modification, as you can see it was not too damaged by the Battery liquid. We Charged the old Battery with +12V just to get between 5 to 6V for testing the PC Board together with the car, this for you which wants to buy new Battery for replacement. If the PC board is too damaged and it do not work, why buy new battery, first you should get the PC board to work.
Charging to between 5 to 6V will take 4 to 5 hours, or you can use a 5V power supply (an old Nokia Charger would do) and connect it to the battery connector, we put a diode between to be sure we do not get any back current the wrong way, just because as we do not have any schema for the PC board we do not know how Volvo has done this and by connecting a diode in serial with the power you protect your power supply. GOOD LUCK!