Hi,

I've been having a problem with the alarm system on my '99 C230 for a couple of weeks. While sitting parked and locked with the FOB, without intrusion, occasionally the lights will flash as if the alarm was going off, but no siren (The siren does in fact work, I've set it off myself).

Yesterday morning I went out to my car to find the lights flashing AND the siren blaring. I had to unlock the car with the mechanical key and get it jumpstarted. (There was enough juice to light up the dash but not start the engine). I took it to a Mercedes mechanic and they told me they suspected the battery has been low from infrequent use, setting off the lights, and finally dropped completely, which might have triggered the whole alarm system. (I told them I thought the alarm system was draining the battery, which is only 9 months old). They charged it up fully and ran some diagnostics, saying they found no draws in the system.

Well today the lights started flashing again, and I took it back and they are starting to believe me that the problem is the alarm system, not the battery. Trouble is they don't know what the problem is specifically, and said they'll research it.

Anyone have any ideas what could be wrong?

Thanks,
Tristen

 

Hi there,
Herew is what I had to go through with my C240 2003. It was going off late light, when temp. use to drop in winter. the light and the siren. I took it to the dealere and dealer thought it is the siren, and that was changed for $450. it took two nights, and the problem happened again, and the dealer wanted to try one more thing, which I gave them for diagnostic and the dealer wanted to charge another $1200 and"could" fix it.To cut the story short, I decided to take my car out of the dealership, but now dealer wanted to charge me another$350 to diagnos the car, with no findings.... I guse what I'mtrying to say, is to take your car to a diffrent shop and install a new alarm, this alarm thing could be really costly,...
Just a suggestion
ken

 

Hell I'd rather have them unplug it. After I jumpstarted it the siren was going craxy on the driv to the dealership. I stopped at a light next to a police car, siren going off, and the officer didn't even look over, so I don't exactly feel like the alarm actually accomplishes anything.

 

My 04 just started acting up about 2 weeks ago. It started when I was driving down the road and I had all the windows open, looking real good in the Benzo! LOL....so the alarm (which sounds like a siren) starts going off. Well I am now stopped at a red light and people are looking at me like WTF?? So I just play cool and get on the interstate and it goes off 2 seconds later, it comes back on. Well this went on 3 or 4 times with in 30 minutes and then stopped the rest of the day. So since then it starts to just flash the lights and no siren. It actually happened tonight.

So one other thing it does now.....the key will not lock or unlock the car even 2-3 feet away from the driver door sensor. So I have to get like 1 foot from the driver door for car to pickup on the function of the key. I thought it may be the batteries in the key so I changed it, but it does the same thing. But the key does it every time, it doesn’t do it intermittently like the alarm but I am pretty sure there has to be some type of coincidence to the two.

If anyway can help please let me know.

Thanks!
04C230K

 

really hard to say but alot of the time its the siren itself that shorts out. or its a control unit failure......your locks not working you should check your fuse for " radio" and see if its blown. also check your AM reception see if there is any. if you have a coupe car you could need a rear glass, or a sedan you could need a "com bar"( a long strip of antennas" which is above the rear glass ...try pushing up on the very back of the headliner right were it meets the rear glass and see if the remote starts working or you radio reception gets better this is just a possiblity. it could be other things too like a bad remote.

 

If the remote does not work except from really close and pointing to the door handle, it is an antenna problem and your IR only is working, not your RF signal. Try a new battery on the remote, otherwise it is a matter for whoever understands electronics.

The siren and lights going off means you have an interfering signal triggering and it could come from your electrical system (fault) or an outside source (signal). Have it also seen by someone who knows.

 

Well I used both remotes and changed batteries and you still have to be right on the door sensor for the key to work. So I know it's not both remotes. Radio is fine. All FM and AM works. Since I last posted the alarm hasn't acted up but you still have to be close to the car for the remotes to work. You can't stay at a distance and lock it anymore. Heck I can't even be on the passenger side of the car and lock it anymore. SUCKS! So not really sure what is going on with it.

 

fuse box under the hood and one in the trunk. did you check them both? have you had tint put on the rear window?

 

Well I haven't checked the fuse box. But why would I check that if everything works? Just not working properly. Well when I first got the car a few years ago it was still under warranty. It wasn't tinted and when I did put the rear Defrost on it would make the FM channels static. So MB replaced my whole rear glass because they said the antenna was interfering. Yes I Had the windows tinted since about a year ago and when I put on my rear defroster the FM channels go static. I never used it much so it wasn't a big deal. Well It started peeling off and turning purple so I had the company redo the rear tint. So I had it redone and about a month or so later this started happening to the car alarm and remotes. So do you think that has something to do with the tint causing interference? THANKS!