w203 alarm no noise or indicators

[runner40]

hello there everyone .i have been trying to resolve an alarm issue on my c200 k 2001 w203 .there is no indicator flash on opening and closing doors and when locking car and leaving open window unlocking from through the window the siren does not sound .i have tested the cable going to siren it does have power .the inside of the car has the red light on the radio and the towing and motion sensors light up red when button is pushed .
i took the old siren of and opened it ,both the battery and the board were corroded i have since bought two used sirens one from ebay and one from a scrapyard both have made no difference ,so my questions are is there anyway of testing the siren to rule them out as the fault and is there another part that controls the indicator flash and siren .i have also checked the fuses but i am not aware of any relay being part of the system .
any help would be great thx in anticipation

 

[runner40]

hello again bought new alarm siren unfortunately still no working alarm ,no flash from indicators no sound from siren ,i have noticed the red light above radio i think its the motion sensor doesnt light up after 15 seconds as it should .but the tilt and can be switched of and on .the radio does have a flashing red light not sure if thats connected with the alarm.
so my question is do i need the siren coded i have fitted a new rear sam about 3 months ago and needed a few things coded srs and something else