R230 Replacement Alarm Siren

[Philedge]

Anyone know of a source for a replacement alarm siren for an R230, other than MB? The part number off the original one is A171 820 25 26. The £100 MB want seems a bit steep for what it is.

 

[television]

One or two have bought similar ones from Ebay but that was some time back, I have not seen the adds for some time.

 

[Philedge]

Hi Malcolm. That's what I had seen looking around on here, Ebay and the web.

Do you know how they work? There are 3 pins which I assumed were +12v, Ov and a trigger that was held high when NOT in alarm condition? Loss of the trigger would operate the alarm off the +12v supply and loss of the trigger and/or the +12 v would operate the alarm off the battery??

I had read a post somewhere that things were more complicated than that with some sort of "comms" over the 3 wires and a power supply??

 

[phillj]

I Recently removed the alarm siren from my SLK230 on investigation it’s much more than a simple siren. There’s a surface mount PCB inside that has a high end microcontroller on board must be doing more than controlling the sounder Main reason they fail is the breakdown of the two internal 3.6v PCB mount back up batteries, they leak damaging the PCB. Don't think you will find any other source than Mercedes or second hand on Ebay and is it worth buying second hand and potentially inheriting the same fault?

 

[television]

Yes its all part of the immobilizer hence the flashing indicators when its at fault and very hard to just fit a 2 wire siren.

 

[Philedge]

I'm £101 poorer now, but thanks for all the replies.

At least I know my back up mechanical key works through opening door/boot to trgger alarm. Siren is LOUD when its out in the open and not tucked up in the arch!!

 

[zenteknika]

Anyone know of a source for a replacement alarm siren for an R230, other than MB? The part number off the original one is A171 820 25 26. The £100 MB want seems a bit steep for what it is.

Hi did you get your professionally fitted? I heard they might need coding in to your car?

 

[Philedge]

Straight forward DIY. Remove NS front wheel and wheel arch liner. Unplug siren and remove with torx bit. Fit new one and reassemble. Simples

 

[ajlsl600]

30 min job. no coding, just maybe clear code for that fault.

 

[Oneryszarf]

Anyone know how to bench test the alarm horn?

 

[sirpete]

Anyone know how to bench test the alarm horn?

Any luck bench testing your horn? My R230 is throwing a code for a bad horn as well, but I've already fixed several damaged wires so I'm not sure if it's the horn or the wiring again....

 

[brandwooddixon]

Any luck bench testing your horn? My R230 is throwing a code for a bad horn as well, but I've already fixed several damaged wires so I'm not sure if it's the horn or the wiring again....

Hi, I don't suspect that you'll get a response as most of the previous posters haven't been seen on the forum for several years.
It might be worth starting a new thread.
What issue is it that you are having?
Note that a common alarm siren malfunction is that the internal rechargeable batteries fail and/ or leak.
These batteries can be replaced, although MB don't sell them there are online retailers who do.

 

[sirpete]

Hi, I don't suspect that you'll get a response as most of the previous posters haven't been seen on the forum for several years.
It might be worth starting a new thread.
What issue is it that you are having?
Note that a common alarm siren malfunction is that the internal rechargeable batteries fail and/ or leak.
These batteries can be replaced, although MB don't sell them there are online retailers who do.

Currently it's just the code that indicates an issue

B1341 Fault In Communication With Component H3 (Alarm Signal Horn)

I bought the SL500 in rough condition and have been working through issues. It was involved in an accident sometime in the past, and I've found several wires that were frayed and torn, so I'm hesitant to assume it's a bad horn. I had a similar issue with the engine fan and accelerator pedal, replaced both and found it was a wiring issue, not a defective part.

I took the old alarm horn out but it visually appears OK. No sign of corrosion on the connector and as far as I can see, the wiring to it seems fine, but I can't trace is back to the point it goes through the firewall.

A wiring diagram would be helpful as well, if anyone had access to one.

 

[brandwooddixon]

Just a point - the battery issue with alarm sirens is internal damage and not seen unless the siren is opened up.

 

[sirpete]

I opened up the alarm signal horn, and it looks like the NiMh batteries inside leaked and corroded the board. I'm pretty good are electronics repairs, but this is beyond salvaging.

Varta batteries are notorious for leaking like this. I've removed a ton of them from 1990's computers.

If your alarm is working, I recommend taking it apart and removing those darn batteries. If they haven't leaked yet then they will be leaking soon. You can either desolder them or cut them off with side cutters.

I tried to heat up the alarm signal horn and pry it open but had to no luck. I ended up using a small reciprocating saw to cut around the seam.

 

[brandwooddixon]

That's a bad one, and obviously the cause of your error message.