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Hi all,
We have just started having an issue with my wifes 2004 171 slk alarm. We parked it up the other day with the roof down and locked the doors. Aabout 30 minutes later we noticed the alarm was going off. tried to turn it off with the remote but it took a few attempts to stop the alarm. As we were inside a shop and using the remot throught he window I didnt think too much about it.

When we returned home and parked up, with the roof closed, the alarm again went off for no apparent reason. Attempts to turn the alarm off via the remote didnt work. The doors would lock and unlock but the alarm kept going.

Eventually it stopped but we were concerned in case it went off during the night so we disconnected the battery. The following day we reconnected the battery and we didnt have another problem until today ( about 10 days afterwards) having had the roof down we parked the car with the roof closed and again after around 30 minutes the alarm went of and we couldnt stop it. Being in town we had no tools to try the battery disconnection so in embarasment we had to drive the car away with the siren sounding.
I think that the fact that we were able to start and drive the car while the alarm was still going off may be pertinent as I would have expected it to have had an immobiliser as part of the alarm system.

The alarm would sound for a while then stop and start again after about a 5 or 10 second pause. I am sure it was just coincidence but my wife adjusted the heating knob and the alarm stopped and we didnt have any further issues all the way home (about 90 minute drive)
I will have to book it into the local indy to have it star checked, hell knows what the likely cost is going to be.

My intention in the meantime was to disconnect the alarm sounder so at least if it went off again we should just get the flashing indicators and no upset neighbours. It seems that others advise that the siren is located under the bulkhead panel requiring removal of the windscreen wipers and cowl however that doesnt seem to be the case with mine. I cannot see any sign of the sounder there although I think the top of the siren could be behind the battery compartment as there is a fan type assembly below the bodywork which looks as though it may be accessed by removing the nearside wheel and wheelarch trim.

I am assuming this is the alarm and not some part of the heating/ac system.

While there are a lot of alarm issues listed in the forum they seem to relate to the R170 model and it seems that the unit in the boot was fitted differently on the R171's, would this be true of the earliest R171's? I had a quick look in the boot, removed the spare wheel and tools but couldnt see the unit that other threads referred to as being a common cause of the alarm failure due to water ingress.
Also I undestand that that issue also affected the door locking system and we dont have a problem with that. The doors work fine via remote, it just doesnt stop the alarm:frown:

I suspect the cause is the alarm siren unit itself given that it wont stop by unlocking/locking the doors and the fact that we are still able to start and drive the car while the alarm is sounding. Also I didnt notice the indicators flashing while we were driving with the alarm sounding although they were flashing when the alarm initially went off.

Any help or advice on what may be causing the issue would be appreciated along with help on disabling the siren until we can get it on a diagnostic machine. Oh and anyone with acess to a star diag machine close to the Hull or York area who would be willing to take a look would be helpful too:wink:

Thanks in advance for any help provided.
 

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Hi all,
We have just started having an issue with my wifes 2004 171 slk alarm. We parked it up the other day with the roof down and locked the doors. Aabout 30 minutes later we noticed the alarm was going off. tried to turn it off with the remote but it took a few attempts to stop the alarm. As we were inside a shop and using the remot throught he window I didnt think too much about it.

When we returned home and parked up, with the roof closed, the alarm again went off for no apparent reason. Attempts to turn the alarm off via the remote didnt work. The doors would lock and unlock but the alarm kept going.

Eventually it stopped but we were concerned in case it went off during the night so we disconnected the battery. The following day we reconnected the battery and we didnt have another problem until today ( about 10 days afterwards) having had the roof down we parked the car with the roof closed and again after around 30 minutes the alarm went of and we couldnt stop it. Being in town we had no tools to try the battery disconnection so in embarasment we had to drive the car away with the siren sounding.
I think that the fact that we were able to start and drive the car while the alarm was still going off may be pertinent as I would have expected it to have had an immobiliser as part of the alarm system.

The alarm would sound for a while then stop and start again after about a 5 or 10 second pause. I am sure it was just coincidence but my wife adjusted the heating knob and the alarm stopped and we didnt have any further issues all the way home (about 90 minute drive)
I will have to book it into the local indy to have it star checked, hell knows what the likely cost is going to be.

My intention in the meantime was to disconnect the alarm sounder so at least if it went off again we should just get the flashing indicators and no upset neighbours. It seems that others advise that the siren is located under the bulkhead panel requiring removal of the windscreen wipers and cowl however that doesnt seem to be the case with mine. I cannot see any sign of the sounder there although I think the top of the siren could be behind the battery compartment as there is a fan type assembly below the bodywork which looks as though it may be accessed by removing the nearside wheel and wheelarch trim.

I am assuming this is the alarm and not some part of the heating/ac system.

While there are a lot of alarm issues listed in the forum they seem to relate to the R170 model and it seems that the unit in the boot was fitted differently on the R171's, would this be true of the earliest R171's? I had a quick look in the boot, removed the spare wheel and tools but couldnt see the unit that other threads referred to as being a common cause of the alarm failure due to water ingress.
Also I undestand that that issue also affected the door locking system and we dont have a problem with that. The doors work fine via remote, it just doesnt stop the alarm:frown:

I suspect the cause is the alarm siren unit itself given that it wont stop by unlocking/locking the doors and the fact that we are still able to start and drive the car while the alarm is sounding. Also I didnt notice the indicators flashing while we were driving with the alarm sounding although they were flashing when the alarm initially went off.

Any help or advice on what may be causing the issue would be appreciated along with help on disabling the siren until we can get it on a diagnostic machine. Oh and anyone with acess to a star diag machine close to the Hull or York area who would be willing to take a look would be helpful too:wink:

Thanks in advance for any help provided.
The OEM siren comes with a battery. My guess is that the battery is failing after so much years. The siren is located between the left front fender and the windscreen behind the battery on the sidewall of the car. It's encapsulated in a metal housing which needs a special kind of torx (theft protected, with a pin in the middle) to remove.
 

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Discussion Starter #3
The OEM siren comes with a battery. My guess is that the battery is failing after so much years. The siren is located between the left front fender and the windscreen behind the battery on the sidewall of the car. It's encapsulated in a metal housing which needs a special kind of torx (theft protected, with a pin in the middle) to remove.
Hi, thanks for that, I have torx drivers but havent seen anything with a pin in it. does that mean that the battery can only be replaced by a dealer or good indy garage. Any idea on cost and is this behavour typical for the failing battery.

Thanks in advance.
 

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Hi, thanks for that, I have torx drivers but havent seen anything with a pin in it. does that mean that the battery can only be replaced by a dealer or good indy garage. Any idea on cost and is this behavour typical for the failing battery.

Thanks in advance.
You can buy them in a good hardware store, no problem. The battery and siren are one integral part about has big as you can hold in your hand. There are lots of them available used. Obviously those batteries are not new either but they may last for a while.
For my R171/2005/350 the part number was: A219 820 32 26 and I paid 60 EUR used.
No, I cannot guarantee that this will solve your problem but you could try to replace it with a known siren in working order from a buddy or other SLK owner to see if the problem goes away.

At this link there is an example of the anti theft torx. I can't remember the exact size needed, sorry. Shop The Hillman Group 4-Pack 1-in Security Torx Screwdriver Bits at Lowes.com
 

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Discussion Starter #6
Thanks all,
I have disconnected the siren which was in the battery compartment, will look for a replacement to see if that resolves the issue.
 

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I noticed that this was an old thread, but how this ended?

Br,
Janne
Since this thread is 4 years old

that poster willydoit has not been back since

Last Activity: 06-05-2015
 

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where can I find some photos of the battery that show its location?
thanks
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The siren and it's backup battery are next to the car's main battery. You'll need to remove the main battery to access the siren and backup battery.
 
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