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Old 02-02-2012, 07:52 PM   #1
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Angry 2002 C240 Alarm problem NEED Help immediately!!

Hello guys,

Been reading the forum for a while now, and now I need your help!

I have a 2002 Mercedes C240 Sedan. Pretty much stock.

Alright,

So, about two weeks ago, I was driving along and it gave me the warning that my hood was open. Pulled over, opened it, closed it, and it still happened. Over and over I would get this warning every once and a while. No big deal.

Then, it started. I park close to my apartment. At night, the alarm started going off. I would use the remote to lock it up, and sure enough..... over and over car alarm. So, everynight for the next week I would have to disconnect the battery. It didn't really happen during the day though (except I'm not usually near my car during the day, so i'm not sure).

So, I read the forums and some people say it's the key needing to be replaced. So, I took my spare key, Then I bought a new set of batteries, replaced them.

No car alarm for a couple of days. Now, i'm sitting at home, and for the past hour, it's been going off a few times every 20 minutes.



You guys have any ideas? I took it to a local repair guy, and he checked the sensors for the hood, they are all there and they are all working.

I need your help badly. Any suggestions?

Thanks for your time guys.
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Old 02-02-2012, 11:03 PM   #2
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Might be the alarm siren itself. They have a tendency to go off when the stand alone battery built in it goes bad.
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Old 02-02-2012, 11:30 PM   #3
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Might be the alarm siren itself. They have a tendency to go off when the stand alone battery built in it goes bad.

How hard is it to replace? What type of battery is it? Where is it located?
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Old 02-03-2012, 12:05 AM   #4
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what about the hood switches going bad or loose connection?
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Old 02-03-2012, 01:06 AM   #5
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what about the hood switches going bad or loose connection?

According to the garage I brought it too, they checked all the hood sensors and they are all functioning. Is the hood sensor and the alarm two seperate issues? Or... when the car thinks the hood is open does the alarm sound?
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Old 02-03-2012, 08:43 AM   #6
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A faulty hood switch may cause it to go off(thinks somebody opened the hood after being locked). The alarm siren has a battery built into it, you can't get it seprate. Its located under the car to the area behind the Rf wheel liner, kind of under the passenger seat leg area, the liner part makes kind of a "L" shape.
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Old 02-03-2012, 09:14 AM   #7
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A faulty hood switch may cause it to go off(thinks somebody opened the hood after being locked). The alarm siren has a battery built into it, you can't get it separate. Its located under the car to the area behind the Rf wheel liner, kind of under the passenger seat leg area, the liner part makes kind of a "L" shape.

Ok, so you think my best bet is to have a tech replace all the hood sensors? If I took it to a MB Dealership, do you have any idea how much it would cost? I've never taken my car there out of fear of insane prices.

Anyway to just disconnect the alarm system completely? Like, make is so the alarm doesn't work (a fuse?)
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Old 02-03-2012, 09:21 AM   #8
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There is only one hood switch, and the siren would have to get replaced to fix. If you take it to a dealer they will be able to tell what caused the last 3-5 alarm activations, so it would be more accurate.
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Old 02-03-2012, 09:22 AM   #9
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Alright. They replaced the hood switch, so I know that's not the problem. I guess my only option is to take it to a dealer. I just feel like i'm going to be paying out of the nose.
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Old 02-03-2012, 09:44 AM   #10
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Does it still trigger if you turn the car lift switch off on the dash?
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Old 02-03-2012, 09:47 AM   #11
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Does it still trigger if you turn the car lift switch off on the dash?

Sorry, what do you mean? Unlock the car, sit in there and hold down the car lift switch and then lock the car back up and see if it goes off?
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Old 02-03-2012, 10:00 AM   #12
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You can deactivate the trembler switch in the alarm for towing purposes. The trembler sometimes goes sick.

If I were you I would pull the fender liner & replace the battery. Clean up everything while you are about it as corrosion sometimes sets into the alarm connectors etc..
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Old 02-03-2012, 10:11 AM   #13
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You can deactivate the trembler switch in the alarm for towing purposes. The trembler sometimes goes sick.

If I were you I would pull the fender liner & replace the battery. Clean up everything while you are about it as corrosion sometimes sets into the alarm connectors etc..

So before I get out of the car, I should just hold down the tow switch for a few seconds, and then it should be fine? Which battery are you talking about replacing?
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Old 02-03-2012, 10:32 AM   #14
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All you have to do is press the anti-tow switch as you get out of the car. You don't have to hold it, at least not in mine. The light will briefly come on and then go out and it's good to go.
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Old 02-03-2012, 10:34 AM   #15
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All you have to do is press the anti-tow switch as you get out of the car. You don't have to hold it, at least not in mine. The light will briefly come on and then go out and it's good to go.

Alright, I wouldn't mind doing that everytime I leave the car. That's better than replacing the alarm. I'll give that a try.
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Old 02-03-2012, 10:56 AM   #16
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Well this will only determine if the tilt sensor is to blame. If it is, then the alarm won't keep going off. If it is not the tilt sensor then this won't fix it. The fact the car gave you hood open warnings is suspect.. even though you say they replaced the hood switch.
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Old 02-03-2012, 12:24 PM   #17
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I emailed my MB dealership, this is what they had to say on the issue:

"
I am responding to the email sent to us about your alarm going off. I think it sounds like it is the alarm siren itself. They tend to go off at random times due to corrosion of the wiring. I would need to get your VIN # of the vehicle to get you an exact price on replacement of the siren. Please send it to me when you have a moment since there are 3 different types of sirens for your specific vehicle. Once I have that information I will be able to proceed with somewhat of an estimate for you although it really should be diagnosed by one of our factory technicians first."


Ok. So, Here is my inquiry. Once he gives me the part number, i'll probably just end up buying it and trying it myself (depending on his quote price). Has anyone replaced it? Difficulty? Any links to a step-by-step? Where is it located (I know you said fender liner...but what is that?) ?

Thanks in advance guys. your really helping.
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Old 02-03-2012, 07:30 PM   #18
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Star does tell you what the last 5 alarm triggers were so that would be interesting to see but it could be BS if the wiring is bad.
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Old 02-03-2012, 09:29 PM   #19
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There is a battery in the alarm unit with the siren behind the fender liner.
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Old 02-03-2012, 09:29 PM
 
 
 
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2001, 2002, alarm, alram, battery, benz, bonnet, c240, car, disconnect, fix, fuse, mercedes, problem, sensor



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