Ml 350 Alarm problems

paul243

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Aug 1, 2017
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slk 320
Hi,
2014 Ml 350
My alarm has decided to activate at random. Even activated when driving . It sounds for a few minutes, stops and then repeats.
I've pulled fuse#203 and no occurrence since but can anyone please advise a cause and cure?
Thanks
 

Petrol Pete

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Hi if it's the same unit as on older MB's pulling the fuse will not work , it has its own built in batteries. on older cars (like my 2006 C class ) the sounder is under the L/H front wheel arch behind the liner .

They are notorious for going wrong and causing all sorts of weird and wonderful faults ...none of which show up in a scan . It's common for folk just to unplug it and forget about it.

If yours is not like that , Apologies.


 
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paul243

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Aug 1, 2017
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Car
slk 320
Hi if it's the same unit as on older MB's pulling the fuse will not work , it has its own built in batteries. on older cars (like my 2006 C class ) the sounder is under the L/H front wheel arch behind the liner .

They are notorious for going wrong and causing all sorts of weird and wonderful faults ...none of which show up in a scan . It's common for folk just to unplug it and forget about it.

If yours is not like that , Apologies.


Thanks Pete
I'll look at that but strange that It's ok now the fuse is out, fuse is allocated to "anti theft system."
Wondered if it might be related to battery or key fob issues, it's keyless entry, also car has two batteries (one auxiliary) Would pulling the fuse have the same effect as disconnecting the siren?
 
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paul243

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slk 320
Thanks Pete
I'll look at that but strange that It's ok now the fuse is out, fuse is allocated to "anti theft system."
Wondered if it might be related to battery or key fob issues, it's keyless entry, also car has two batteries (one auxiliary) Would pulling the fuse have the same effect as disconnecting the siren?
Ps If it's disconnected and has it's own batteries then in theory it can still sound even on the bench? Or am I missing something?
 

AMGeed

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A new alarm siren is around £100 and a simple DIY job.
Double check the location before pulling arch liners out.
 
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paul243

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slk 320
Thanks, until I get a siren, can it be triggered without the fuse in place, it hasn't sounded since I removed the fuse
 

fifermerc

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Apr 23, 2017
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E350
I had the same issues with my E350 - alarm would go off randomly, sometimes when the car was parked, other times when you were driving. At the time I was too busy to look at it myself, so foolishly had it looked at by my local MB dealer. Problem fixed by replacing the siren unit, total cost approximately £450.
Two years later, same thing again. Having been bitten once, this time I tackled it myself. Removed the left front wheel arch liner, fiddly but not difficult, and located the faulty siren. I decided not to bother with the replacement unit as I guessed I might be facing the same issue in another couple of years, so I disconnected the unit and binned it.
I guess if the car was to get stolen my insurance company might get a bit snippy about the lack of alarm, if they were ever to find out, but that's a bridge to be crossed if and when...
 

Petrol Pete

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Paul . I have actually done the 'disconnect and forget' thing on a 2006 C class (not mine) and 4 years later the car is still fine . The only thing I can think of is that with removing the fuse the internal batteries have gone flat and thats the end of it.

I would still disconnect it (as per video) just to take it out of the loop for ever. Or buy a new one .
 
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paul243

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slk 320
Paul . I have actually done the 'disconnect and forget' thing on a 2006 C class (not mine) and 4 years later the car is still fine . The only thing I can think of is that with removing the fuse the internal batteries have gone flat and thats the end of it.

I would still disconnect it (as per video) just to take it out of the loop for ever. Or buy a new one .
Thanks, Best!
 
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paul243

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Are the internal batteries recharged via the fuse?
 

Petrol Pete

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OP . Just unplug it before it starts causing problems. The one I removed had the owner going into the garage first thing in the morning (on more than one occasion) to find the car had unlocked itself and hazards were flashing weakly as the main car battery had been flattened by the hazards going for a few days .

Not great if the car had ben parked out on the street.
 

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