Hi Guys,

After my experience with the alarm going off randomly I agree with what 180 is saying. My theory though is that replacing the main vehicle battery might just delay the return of the siren tripping.
I think there might be two failures of the siren module.
(1)The batteries inside the siren seem to go through a charge / discharge cycle automatically I think its possible that when the batteries start to fail in the siren it pulls more amps than the alarm is expecting and therefore triggers itself ie only when its armed.
(2) a short in the charging circuit that can occur anytime leading to it sounding whilst driving.

Which fault you get at any point depends on which bit of the circuit board is being eaten by the battery acid at the time!

A new vehicle battery MAY just provide enough amps so the drain caused by a failing alarm battery is not detected but it wont help the sounding whilst driving faults.

Get the siren taken out and either replace it with another one from MB ( in the UK MB say they always have stocks because they keep failing) or rip it apart and hope its not too badly corroded and can be "repaired"


BBlanchard, my siren sometimes didnt work then suddenly started working and wouldnt stop!

Matt