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1999 SL500, 2004 SL500
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32 Posts
Discussion Starter · #1 ·
I have a 2004 SL 500. The alarm Siren goes off on its own, while driving and also sitting and turned off. At first I thought it was the service battery, how ever after charging it (it's only 18 months old), the siren still sounds sporadically while driving. The dealer said I needed the alarm replaced at a cost of $395.00 for parts and one hour labor. Could anyone please tell me where this item is located so that I can replace it myself. Thank you.
 

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1999 SL500, 2004 SL500
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32 Posts
Discussion Starter · #2 ·
Here I am...Posting to my own post.....

My alarm just started this "chirping" thing and then it turns into a full alarm, and then it seems to reset itself. This has happened while turned off, locked and parked. Also while driving down the freeway, sitting unlocked and parked, and sitting while turned on and at an idle.
The service battery (the secondary battery in an SL) was replaced 18 months ago.
It seems that if I put a charger on this battery while sitting, the alarm turns off (or maybe just hits that recycle phase and resets itself). Also, when driving if I turn off the radio, fan, etc. and allow the engine to rev higher it quits ( or maybe again just resets itself).
With that said, I would think that it would be the service battery. Even though it is not that old.
However, after going to the dealer, they said it's the alarm....such that I have also read different times over in this form.
So now, I have taken the front driver side wheel off, the inner fender covering, and have located and removed the alarm.

Now my thought is this: Do I spend $135.00 on an alarm...or twice that on a new service battery?
 

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2012 E350 4matic wagon 2013 SL550
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61 Posts
AlARM

Hi Had the same issue with my alarm. There is a backup battery in the actual siren. Don't remember why. When it fails the alarm will go off out of nowhere. Like at 3 in the AM Replacing the siren solves the problem. Good Luck
 

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2003 Mercedes Benz SL500
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1 Posts
2003 SL500 Alarm issues

I just bought this beautiful car - 2003 Merc Benz SL500, used, private party. Only 60K miles, and everything is like new. I LOVE the car!! Only snag - the alarm seems to be problematic, perhaps it's the wrong time of the month for it? :) Seriously, it sounds without any apparent reason - the car will be parked, and suddenly, there she goes. Loud, lights flashing. Sometimes it will just be the lights flashing. It sounds like the antitheft alarm. And then, this one time, it sounded like a chirping sound. Started slow and soft, and then grew loud and fast!! Mostly though, it sounds like the normal antitheft alarm. The antitheft alarm-sounding alarm only comes on when the car is switched off. The chirping-sounding alarm also came on that one time, even after I started the car and was driving it. W.t.f.?
 

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1999 SL500, 2004 SL500
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32 Posts
Discussion Starter · #5 ·
Siren

For the most part I have found that it is either the service battery or the siren. If your service battery checks out then go after the siren. It's probably located inside the driver side front fender, behind the inner fender covering, in the upper rear corner. From what I am told, there is a backup rechargeable battery in the siren itself. It is sealed however and not worth the time to try and replace. Besides, if you have taken the time or spent the money to get to the siren itself, you might as well replace the whole thing and save a headache later. If you don't want to spend the $135.00 on a new siren (part cost only there) then just unplug it, tape up the ends and put it all back together. ....Really, ...do you need that stupid siren anyway?
 

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1999 SL500, 2004 SL500
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32 Posts
Discussion Starter · #6 ·
I just bought this beautiful car - 2003 Merc Benz SL500, used, private party. Only 60K miles, and everything is like new. I LOVE the car!!
FYI.... Not to give you any bad news but, have you checked to see if the gas tank in your new/used SL has ever been repaired or replaced?
The 2003 and early 2004 SL's have a problem with a baffle inside the tank coming loose and making a dinging, rattle, or banging noise. It's a $2,500 to $3,000. Fix at the dealer. I've researched this quite a bit because my '04 just started to have this problem (84,000 miles). People will tell you that the tank has to come out the bottom of the car...which is false. I'm doing it right now... It comes out the top. It's a pain in the butt, and you have to dismantle most of the rear interior area and forward area of the trunk. Then you lift the tank out the top.
Anyway....blah, blah, blah...that's all for a different post.

Just be advised...it's a known problem.
 

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Hi guys, I have a 2003 SL500 which is a great driving car when its driveable. Been having major problems with the alarm system. I was in the shower when it started going off for no reason. not its active and it wont allow me to start the car. At times the serin goes quiet but the lights flash and the car wont srart. need help badly.
 

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2005 R230 SL350 (M112)
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283 Posts
In my 2005 a brown 7,5 amp fuse in the fuse box under the bonnet driver side (rhd). It is the 3rd fuse in the row, don't remember from front or rear, but the 7,5 amp will tell.
Be thoughtful when replacing the lid on that box. Clean seal, proper fit, properly locked with the slider. There's a lot of rain/washing water coming though the louvres right above it.
 
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