R170 SLK alarm lunacy

Benmac

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Right, I have a bit of a major issue with the alarm on my wife's SLK (230 '03). Last night after she returned home noticed the aarm was going off. Out to turn it off and no joy. Car would unlock happily but thealarm just kept on. The alarm noise was a sort of distorted version of the clear alarm signal. But it was certainly loud enough.

After various bits of faffing I had no option but to disconnect the battery. Left it for a while and reconnected. Reset the ESP and the radio code, locked it up and all seemed well.........for about 10 minutes then it started again. This time I yanked the fuse which had the same effect. Only problem this time being that the doors were now stuck open (couldn't turn the key in the lock or push the button down). To allow the car to be locked overnight I opened the bonnet, then locked it then pulled the fuse. Closed the bonnet on a rag so that it doesn't shut.

For a while the boot catch sensor has been playing up basically thinking it isn't closed so beeping at you merrily. I cleaned this up which helped but its come back in recent days. Just wondering if the two are linked.

Any ideas?
 

Alex Crow

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there are two likely culprits here, the alarm siren can fail giving you constant false alarms - the noise you describe suggests this. also the pse unit in the boot which controls the alarm and locking functions can get water in, this is an all too common and expensive problem! to check the pse unit remove the jack next to the spare wheel and lift out the plystyrene tray that it sits in. you will now see the side of the foam encapsulation that contains the pse unit, is it damp at all? you can carefully remove this foam cover and unit together, although beware the wires and pipes, dont pull too hard! what you are looking for here is ANY signs of damp, current or historic, if it is damp start saving up for a new one. the alarm siren can be unplugged, and should not cause further trouble if this is the problem.

do the interior lights come on/go off with the doors?
 

television

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I also think that this could be water in the PSE but this is a late car, there again so much rain of late.
 
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Benmac

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Hmmm, thanks chaps. I'll have a look this afternoon. Just for my ears when I'm tinkering I may disconnect the siren, is it easy to get to, sems to be under the trim at the base of the screen, didn't poke around too much last nightas it was dark and the battery disconnect seemed the best bet.

Yes, the interior lights work fine (when I haven't pulled the number 10 fuse out to shut it up).

Regarding water, well, it had just done a long trip in the rain so...........
 

television

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It is hard to give a good answer at this stage often when the rear PSE pump is damp /wet the indicators play up as well

Just let us know as soon as possible on this point
 

drmw

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The alarm noise was a sort of distorted version of the clear alarm signal. But it was certainly loud enough.
Any ideas?

Had a very similar experience last / this week on an SL - not all these symptoms but the one above exact - turned out to be the siren (aka controller according to the packaging) - replaced, all behaving itself now.

Part cost £62.00

Hope yours is as simple!
 
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Benmac

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OK, I had a look at the PSE and without pulling it out had as good a poke as I could. No evidence of any water as far as I could see and the foam around it was cold but dry to the touch.

Popped the fuse back in as I was going to be around and kept my ears open. 2 hours later a brief chirrup and then off it went again. Out came the fuse and all was peaceful.

During all this I had phoned the chap who looks after my Exige as he did his apprenticeship on MBs. Luckily two of his mates from his MB days have just set up on their own as MB specialists (40 years experience between them) so today I've taken up to them (of course it has behaved impeccably all morning). They're going to have good look but on first inspection they suspect the siren unit rather than the PSE thankfully. Fingers crossed.
 

television

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Hopefully it will just be the siren then :D:D
 

Alex Crow

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the alarm siren was making odd noises, this alone suggest a fault there. your locking and interior light sare ok, the pump foam is dry - happy days, looks like a siren!
 

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Some folk are opening them up and replacing the batteries wit a good success rate, with others it is water in the siren
 
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Benmac

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Yep, it was the siren, phew. Diagnosed and fixed today. PSE is in rude health. Got the chaps to give the car a good look over while they have it as I haven't been happy with the dealer's service attention to detail and they've found a broken exhaust bracket and a weeping PAS pump as well so they're going to see to those while they have it.

All for a price less than the dealer would have charged to look at it for 5 minutes no doubt. Happy days.

I'm genuinely impressed with these chaps. Not sure what the advertising permissions are on here but if anyone is looking for a specialist in Lancashire feel free to send me a message.
 

television

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Yep, it was the siren, phew. Diagnosed and fixed today. PSE is in rude health. Got the chaps to give the car a good look over while they have it as I haven't been happy with the dealer's service attention to detail and they've found a broken exhaust bracket and a weeping PAS pump as well so they're going to see to those while they have it.

All for a price less than the dealer would have charged to look at it for 5 minutes no doubt. Happy days.

I'm genuinely impressed with these chaps. Not sure what the advertising permissions are on here but if anyone is looking for a specialist in Lancashire feel free to send me a message.

Please put the info up :D:D
 

drmw

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Some folk are opening them up and replacing the batteries wit a good success rate, with others it is water in the siren

Mine has clearly never had any water contact so probably just the battery - it's sitting at home so if anyone wants to try a little DIY to help someone in need when the next such post goes up, just PM me you address & I'll post it off, no charge :D
 

television

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Mine has clearly never had any water contact so probably just the battery - it's sitting at home so if anyone wants to try a little DIY to help someone in need when the next such post goes up, just PM me you address & I'll post it off, no charge :D



Yes please and I do this for other members and I can do a DIY PM on the way :D
 
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Benmac

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Please put the info up :D:D

Pleasure.

Read Garage Limited
The Filling Station
Whalley Road
Read
BB12 7NZ

www.readgarage.co.uk

01282 777731

Run by two chaps with about 20 years MB experience each, Sean and Peter. Taking the car in there was a joy. No teeth sucking just confidence that they knew what is was likely to be and that it would be fixed.
 

DJC013

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Hello, glad that you gort your car fixed !! Do you know where the Siren was located ? Regards Damian. :)
 
W

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Wildhog

I too have had the 'Middle of the night' spontaneous alarm probs. I had this a few years back, but it just went away and was fine? Thanks to your tips, I was able to locate the PSE unit which seemed dry and around it was dry, so I removed the siren as a temporary fix, with a view to opening it as per the instructions and testing/replacing the battery.
2 questions - Could it possibly be the Main Car battery that is making a voltage drop trigger the alarm? I put a meter across the terminals and got 12v (Engine not running), I thought for a healthy battery you got 13-14v ? also, where is the fuse to just isolate the siren? I looked at both fuse boxes and found nothing.
BTW the door locks all work fine, the interior lights go on/off ok, all works fine until I set the alarm and 5-10 min's later, it activates the alarm. Well, not anymore though as the siren is in my garage :) Any thoughts on the battery voltage would be appreciated. Thanks.
 
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Addition to prev post for Wildhog

Sorry forgot to add, the Alarm Prob is on a Beautiful SLK R170 2001 'facelift' model in Magma Red :D
 
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