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Alarm / Siren Issues : Goes off for no reason/Kills Battery FIX DIY..
So the newest issue my car has been having, is that when i lock the doors with the smartkey, about 20 secs later my alarm sounds for no reason, and then the tow away lights begin flashing. At 1st i thought, maybe the rear battery is going, then i thought maybe water was getting into my trunk and shorting the pse pump, and lastly i thought maybe my rear SAM was going bad. Luckily for me, it happens that the siren (mounted beneath the driver's side fender) contains its own 2 batteries, and these go bad. When they go bad, they leak battery acid all over the board, corroding it, and leaving you with these issues : everytime the alarm is activated, the siren will sound soon thereafter. The car thinks its being towed/stolen...
Its easy to fix, just remove left front wheel, the rear part of the inner fender liner, and then reach inside (under the fender) and remove the siren. I decided to remove it with the bracket (3bolts as it seemed the easiest). You can buy a replacement from parts.com for 103.00. I left mine out until i decide if i really want to spend 120.00 shipped on something that is useless. I can always order it, and install it in under 20min if i want to later.
I found many other MB owners have the same problem as i think the siren is the same for the entire mb line of cars (pertinent years).
I have a bunch of pics i thought you guys might wanna see that show the damage.. I sawed the siren in half, just to take a look...
Thanks to the previous poster for solving the problem for me!
The local cost of the siren was AUD$400, I ordered one from Pelican Parts in the US for AUD$218 delivered. A bit more expensive than parts.com but they do deliver internationally and the jelly beans were a cute surprise.
In the three weeks it took to arrive the alarm siren was going off intermittently most days and driving me nuts. If you unlock the car with the remote (from inside the office) the car locks itself again 15 seconds later and the alarm goes off again. If you don't unlock the car the lights keep flashing until the consumer's battery goes flat.
The replacement procedure is as follows:
Don't start unless you have a 1/4" drive metric socket set and a set of tamper proof torx bits
Jack up the car and remove the left front wheel
Remove numerous screws that secure the inner plastic mudguard liner. Its tricky to pull it out.. just keep poking and yanking and it will eventually crumple out
Remove the three nuts that secure the alarm shroud in place. the one at the back is a bit of a pain
Withdraw the shroud and siren
Undo the torx bolt that secures the siren
The new part requires an 8mm nut which you will need to get somewhere
Replace the siren in the shroud with the 8mm nut
Replace everything in reverse order
It took me about 30 minutes and I had to scrounge a nut from one of many "spare nut and bolt just in case tins"
One difference with the new siren is that it beeps once when I lock the car and three times when I unlock it
I don't know if that's a new thing or if the old one was just stuffed
The photos tell the story
That's nasty damage to the circuit board (two photos next post). What a stupid design... when a $2 part inevitably wears out it kills a $400 circuit board
It hasn't gone off yet!
Peter
Last edited by cowiepeters; 11-17-2013 at 03:11 AM.
old thread, but just wanted to confirm that corrosion of little batteries inside siren will effect siren circuit board and cause siren to go off randomly. i removed the siren by pulling off inner fender on left side to access and then unbolting. i then tried to seal up the connector plug to prevent water from entering it and then put inner fender back in place. this solved my problem and i dont have any dash lights or any other problems of which i am aware other than not having a randomly firing siren. i did not pull codes with sds since i dont have that machine. here is image of circuit board. -->
that brownish black **** in middle of green batteries is corrosion that hoses circuitry.
This seems to be a prevalent problem on Mercedes cars. I wonder why they did not set up the horn with replacement batteries instead of fixed. Seems to be a bit of short sightedness.
This seems to be a prevalent problem on Mercedes cars. I wonder why they did not set up the horn with replacement batteries instead of fixed. Seems to be a bit of short sightedness.
Planned obsolescence? Guaranteed parts and repairs for dealers? Some **** conspiracy? German over engineering? The answer is here somewhere, but at least we know how to fix it!
The part number is shown in photo 1 of post #3 above.
Unfortunately, those images display no bigger than thumbnail....enlarging by zooming my browser page distorts sufficient enough to render part number illegible.
Unfortunately, those images display no bigger than thumbnail....enlarging by zooming my browser page distorts sufficient enough to render part number illegible.
Double click on the image, then select "Download" and it is displayed full size. To make life easier for you - here is p/n from that picture A219 820 32 26. Hope I have read it correctly (label is upside down in the picture).
Double click on the image, then select "Download" and it is displayed full size. To make life easier for you - here is p/n from that picture A219 820 32 26. Hope I have read it correctly (label is upside down in the picture).
Weird, at some sites that part shows up as NOT for my 2000 S430, but at Amazon it lists my vehicle as a match. Have purchased (received within 14 hours! Yes, I am a Prime member) and eager to swap in. Thanks to everyone who has contributed to this thread!
I just got the chime replaced on my w219 2006 cls500 because the noise had gone and I knew it was getting ready to die. I had the dealership put a new one in and it's like I opened a can of worms. Now I am getting the random alarm going off which I never had before. Immediately after they installed the new chime it was so quiet I had to put my ear on the hood to hear it. So right back in the den it went. Finally it was ready and they told me they had to run a wire from the unit to my rear sam. About a week after this the thing goes haywire and the alarm will not shut off even when I turn the car on and drive for blocks.. It finally dies or shorts out. SO back to the damn dealership I took it. This time they say it was defective.. and when I come to pick it up surprise the same faint chirp noise (they really don't give a damn at this dealership). I pointed it out and a mechanic looks at it right away this time. He is able to restore the sound in about 10 minutes and tells me he adjusted the volume and that it was set to 20% (not sure if this is bull**** or what). It's been a few more weeks and haven't had any major meltdowns but every once in a while the alarm will go off when I lock or unlock the car but i've been able to turn it off. I hope the dealer didn't screw up my rear sam unit or damage the electrical system. Because I'm seeing new random warning lights accompany the alarm like the rear license plate light.
I picked up my 2007 SL550 in July 2017. When I locked/unlocked doors, the lights would flash but I never heard a beep of any kind. Then about 2 months ago I started getting the 1/3 beeps when locking/unlocking. I thought it was odd that it had never worked before, but then started working on it's own.
Fast forward to about 3 weeks ago and my alarm goes off randomly when the doors are locked. Not sure how soon after locking the doors but it goes off again and again until I leave doors unlocked.
I'm hoping the solution above will fix my issue. I'm going to pull the siren tomorrow and inspect. I really don't need the alarm, as others have said it's pretty useless...but I don't want my battery drained.
IF you remove the alarm will you still be able to lock the doors? Can it still make your battery flat? Thinking of removing the alarm for now until i get around to ordering a replacement.
Yes (you can still lock the doors). No (it will not drain the battery if removed, but there is no guarantee that some other part won't drain the battery).
Yes (you can still lock the doors). No (it will not drain the battery if removed, but there is no guarantee that some other part won't drain the battery).
Hi, I know this is an old thread but need some advice. My partner has a 2000 clk 320 and left it standing for a while so battery died. He had to change some pump thing in the boot ( sorry, I’m no car expert) and he’s also put in a new battery today as alarm kept going off. The problem is that when he connects the new battery the alarm still keeps going off and now also the front windows are down and can’t go up. Obviously the immobiliser has kicked in so smart jet won’t go in. He’s about to lose his rag with this car so really need some advice. Could the alarm be faulty and should he just remove it. Will that fix the immobiliser and window problem or is it something else? I have attached pics of the pump he fitted.
2005 R 230 SL350 (M112 3.7). Sold the 1966 W113 230SL recently
Originally Posted by John Macintosh
Fixing the Mercedes siren module (DIY):.
That’s a nice idea. I have two questions:
- when gunk from leaking batteries has spoiled over the pcb it would be a good idea to test if the thing still works at all. I’d think there’s more intelligence in there than just two batteries and a horn. Is there a way to test the unit on a work bench?
- I would be tempted to lengten the wires and put the batteries in a more convenient place. Behind the louvre in the fender (is there a cave in there?) perhaps, or under the hood or dash. Any thoughts?
Unless the PCB (printed circuit board) is very corroded from the leaking batteries, it should be fine. I suppose that a $10 to $15 dollar investment (for batteries) is well worth the try compared to buying a new or refurbished siren module.
The wires from my PCB were about 6 inches (15 cm) long. This gives you ample length to solder them to your battery wires. The batteries fit very nicely under the siren (speaker portion) within the metal bracket that holds the siren module.
My repair has been working great.
Last edited by John Macintosh; 05-24-2019 at 08:31 AM.
06-09-2015, 01:01 PM
