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Discussion Starter #1
Hello everyone,

I am so frustrated with this alarm problem. I have researched forums and checked all the items they have suggested. I have now hit a dead end and my alarm keeps going off randomly. There are days where it can go without going off and then out of nowhere it starts again.

I have checked the PSE pump, #9 fuse, car battery, Key fob battery, replaced the alarm siren, etc.

Do you have any other ideas/options?

I was thinking my last options are the alarm module behind the PSE pump or just a STAR system alarm reset?

What do you suggest?

Thank you.
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Discussion Starter #4
I replaced the alarm siren unit, the one that is located under the plastic windshield wiper cover.

The weird thing is that if I leave the window down, lock the car, and then open the door from the inside, the alarm does not go off and just unlocks like if I pressed the key FOB.
 

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Super Moderator UK SLK 55 AMG 2007
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Have a look at the vacuum lines from the pse.


You've already checked the pse and if that's ok then maybe the line is twisted.


Hope you're good at yoga, because it's a bit of a contortion trying to see.
Yellow tubes in pic below: (ignore the red arrows, borrowed pic)


 

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Discussion Starter #6
No, nothing dangling from rear-view mirror.

Bit of background: Someone hit the rear-end of the car a month ago. The taillight was broken and so it had to be towed. I suspect that the tow truck driver did not disable the tow alarm when it was getting towed to the body shop and the alarm just kept going off. Do you guys think that the alarm system stored all the alarms and it has just gone crazy because of that event?
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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you say you checked the car battery?
but how old is it?

the slk needs a great battery, not a good battery otherwise all types of electronic gremlins start to appear
 

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I had exactly the same problem August before last. It would go off for no reason at all. I stored it that winter and in January, decided to take it out for a spin. The battery was nearly dead so I replaced it. Haven't had a problem with it since.
 

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Discussion Starter #10
Thanks Avel Du. I will give those threads a read. There is and SLK320 at my local scrap yard and I'm tempted to go remove the tow sensor unit... hopefully that will fix the problem.

jbanks15: I'm not sure how old the battery is... I took it in to a shop to get it checked and they said it was at 50%. They charged it and after installing it the alarm did not go off for 3 days. I took the battery back to get it checked to see if it had lost charge, they checked it, but it was at 100%. At this point I discarded the battery as being the problem. But, now that you mention the battery, I might have to go check again. It is not an original Mercedes battery in there, it's one of those Duralast (it came with the car).
 

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Remember, batteries get bad cell or cells
They get charged up, act ok for a while, then go bad.
You need to get a conductive test done on the battery
does the battery have a sticker with date manufactured on it?
 

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Discussion Starter #12
I think I might just replace the battery with a new OEM, since I don't like seeing that Duralast in my engine bay anyway.

I will report back on the results later.

Thank you all for your help. :)
 

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Discussion Starter #13
Hello everyone,

I purchased a new oem battery. After 1 and a half weeks, the alarm had not gone off until today. At this moment, I think the only option left is to take it in to the dealership to hook up the STAR Diagnosis and see where the alarm is being triggered.
 

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Super Moderator UK SLK 55 AMG 2007
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Hello everyone,

I purchased a new oem battery. After 1 and a half weeks, the alarm had not gone off until today. At this moment, I think the only option left is to take it in to the dealership to hook up the STAR Diagnosis and see where the alarm is being triggered.

Check the battery and see that it hasn't lost it's charge.
It might be that you have an electrical leak that is drawing power when your car is parked.
Several threads on here about that.


The fact that it was ok for a week and a half suggests battery drainage.
 

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Yup, I agree look for a current drain. I remember my family would have that alarm issue and the culprit was the battery going bad. This was on a few Bimmers & an Audi which should be similar to our cars. I hope you find the problem.
 

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Discussion Starter #16
Update -

No power drain whatsoever. The battery is 100%

I took the car back to the body shop that fixed the car (the alarm problem started after they fixed it). The body shop took it to a Mercedes "guy" and the alarm system got re-calibrated (???), it was fine for about 4 days. I took the car for a drive and stopped for some coffee and the alarm started going off again like crazy.

Took the car back to the shop and they said that they might just have to take it to Mercedes to figure out the problem. They did mention that this has happened before with some of the vehicles they repair.

Will update on the problem when I get it back.
 

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Discussion Starter #17
UPDATE -

Alarm still going off. The car went to a Mercedes "specialist." He diagnosed the problem as the alarm siren under the wiper spindles. I told him that the part had been changed already. To test out his diagnosis I unplugged the alarm siren altogether. I don't believe this is the problem because the lights still go off even with the alarm siren off. The lights go off randomly, sometimes when I walk out to the garage they are going off, just like they would have with the alarm siren off.

Any other ideas? Maybe setting the car on fire?

Thanks.
 

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Well I think I am haunted by the same 'ghost in the machine'. Lights started flashing for no apparent reason, a few minutes after locking the car (2001 SLK320). I decided the sixteen year old battery in the alarm siren might be due for a replacement so I opened it up and replaced it, which was not easy at all. I guess I did fix the alarm siren; a few days later the light show was accompanied by a surprisingly loud siren, at about 6am on a Sunday morning.
I took a closer look at the PSE pump in the trunk, which was actually the first thing I checked, but then there had been zero signs of wetness around the pump or anywhere in the trunk for that matter. And the central locking has always worked flawlessly. But when I unplugged and inspected the black and the white connectors on the pump I saw very noticeable corrosion. Somehow water managed to get deep into the connectors and nowhere else.
I cleaned the connectors on the wiring harness, and removed the PSE pump and opened it up. Fortunately there were no signs of corrosion anywhere but the connectors so I cleaned them too. I put it all back together and bagged the pump to reduce the chance of it getting wet again.
Forgot to mention, ever since I bought the car there was a faint glow from the light on the anti-tow-away-override switch on the dash. I thought for sure my PSE pump connector cleanup would cure that, but no. If anything, it's a little worse; even throbs sometimes. So I unplugged the black connector on the PSE pump and the light went off. I bet that disabled the alarm completely, but at least the central locking still works (unless you unplug the white connector). I've gone a few days now without disturbing the peace. For for now at least until I stop being pissed off, I will run around with the black cable off. And shop for a PSE pump.
 

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Discussion Starter #19
Dean-O:


YES!!! That is exactly my problem, we are being haunted by the same "ghost." Thank you for your input on this issue. At the moment I have unplugged the #9 fuse so the lights don't go off, but I do not have central locking, interior lights, etc.

I think I will also follow your footsteps and disconnect the PSE pump black wires so I can have central locking again. I guess I will also have to start looking for a new PSE pump :/

Once again, thanks a million!
 

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Help! Alarm keeps going off randomly.

My battery went dead on my SLK 230 recently because I wasn't driving it regularly. My battery was totally dead, so I got it replaced under the 5 yr, warranty (battery). However, the alarm (security) keeps going off intermittently when I try to drive it. No problems before the battery died. Will this problem go away after fully charged up driving it again, or do you think it is a sensor problem. please help! Thanks so much! :) Letha
 
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