W212 Siren Woes

[TeddyRuxpin]

Hi,

I have a W212 that has been on/off chargers for a while and not used 'properly', and now after being locked the indicators go off and the interior lights go on. I'm aware that this is usually down the alarm siren battery issue. I'll likely just change the whole thing at one point.

Currently I have it locked with the key but the alarm is off and it's sat on a trickle charger. I also got an 'auxiliary battery malfunction' fault even though I'm pretty sure these early W212 cars don't have an auxiliary battery. Anyway, I am assuming that the fault is the alarm siren located behind the front passenger wheel arch.

Is a 'quick fix' possible by simply unplugging the siren? Yes I know that the alarm will then not sound if there's a problem, but I've read a few posts that lead me to believe that simply disconnecting the siren will stop the issue with the hazards etc until I can sort it properly.

Cheers!

 

[OneForTheRoad]

Hi,

I have a W212 that has been on/off chargers for a while and not used 'properly', and now after being locked the indicators go off and the interior lights go on. I'm aware that this is usually down the alarm siren battery issue. I'll likely just change the whole thing at one point.

Currently I have it locked with the key but the alarm is off and it's sat on a trickle charger. I also got an 'auxiliary battery malfunction' fault even though I'm pretty sure these early W212 cars don't have an auxiliary battery. Anyway, I am assuming that the fault is the alarm siren located behind the front passenger wheel arch.

Is a 'quick fix' possible by simply unplugging the siren? Yes I know that the alarm will then not sound if there's a problem, but I've read a few posts that lead me to believe that simply disconnecting the siren will stop the issue with the hazards etc until I can sort it properly.

Cheers!

You probably already know that the siren has its own built in battery that when dying tends to give false alarms .

Unplugging it will most likely kill any false alarms also.

 

[TeddyRuxpin]

Aye, but from reading around I was under the impression that at this age it’s likely that the batteries have leaked all over the inside of the unit and corroded everything. Perhaps that’s not the case?

I’m also looking for a ‘quick fix’ to stop the lights flashing issue

 

[OneForTheRoad]

Aye, but from reading around I was under the impression that at this age it’s likely that the batteries have leaked all over the inside of the unit and corroded everything. Perhaps that’s not the case?

I’m also looking for a ‘quick fix’ to stop the lights flashing issue

I thought that's what I said . I took one apart on a car I once owned ( forget what it were now ) as it was keep giving out a very low muffled beep , inside was just all rusted up , the PCB was brown tbh from water ingress. If it's not the siren giving false alarms ,you'd have to ask what else can it be , ultrasonics inside maybe ??

 

[Petrol Pete]

Just un plug it , nothing happens.