W203 coupe Alarm beeping on setting issue

[ABravo]

I am a new member .My daughters w203coupe 2002 was recently in a very minor collision to rear. It was left at the garage for 3 weeks and the battery was flat. I have fully charged it. Now When I set the alarm now it beeps 3 times and once when I unlock it. This never used to happen. The boot bulb was also blown, I haven't replaced this yet as only got car back tonight. Is the beeping a warning there is a problem with alarm.? The doors/boot are definitely closed when setting alarm. If I leave door/boot open and set alarm it beeps for longer, this is why I think it is a warning. Could it be the batteries in siren going. A faulty sensor damaged in accident?
If you can help I would be grateful, I am loathe to go to the main dealer as they charged me £1000 for a new key and resetting something last time. Please help

 

[markjay]

Alarm beeping when set is usually an indication that the internal NiCd batteries inside the alarm sounder are failing.

The internal rechargeable NiCd batterers are there to ensure that the sounder will work even if the thieves disconnect the car's battery.

Officially the sounder is a sealed unit and need to be replaced, but in practice the unit can be opened, and suitable new NiCd batteries sourced and re-soldered onto the PCB.

Said that.... given the accident, I do not not know if the issue is indeed that of the faulty NiCd batteries, or something else as you seem to suspect.

 

[markjay]

See also:

Mercedes C Class (W203) Alarm Problems - Mercedes Gen-In

 

[ABravo]

Thanks for feedback. Following research I hope it is just siren. I remember her saying the alarm started going off on its own. She thought she had maybe left boot open. Will see how much Merc want for a new one, it seems straight forward diy job. Thanks for link I had found that. Cutting and soldering maybe too much for me, but if I can source batteries it would be a very satisfying outcome. . Thank you for help.

 

[Dec]

That alarm might be ok, you should test the alarm by intentionally triggering it, when triggered, the siren should sound for 30 seconds and the hazards should flash for 3 minutes.

It is normal for the alarm siren to chirp 3 times when locking and once when unlocking, this is the normal default factory settings, the fact that the siren didn’t chirp before and does now could be because the siren reset to factory default because the siren batteries were deprived of 12v for 3 weeks.

In any case, if you do replace the siren yourself then it will chirp as described above unless the chirps are turned off with STAR.

Dec

 

[ABravo]

That alarm might be ok, you should test the alarm by intentionally triggering it, when triggered, the siren should sound for 30 seconds and the hazards should flash for 3 minutes.

It is normal for the alarm siren to chirp 3 times when locking and once when unlocking, this is the normal default factory settings, the fact that the siren didn’t chirp before and does now could be because the siren reset to factory default because the siren batteries were deprived of 12v for 3 weeks.

In any case, if you do replace the siren yourself then it will chirp as described above unless the chirps are turned off with STAR.

Dec

Dec
Wish I had read this before buying new siren. I have deliberately triggered the alarm, it sounds for about 5 seconds and indicators flash. The indicators continue to flash continuously for about 4 mins when they are flashing it appears the alarm has reset after 30 seconds as it will sound again if triggered even though the lights are still flashing.
Question .it only sounds for 5 seconds do you think
that it is not completely broken but on its way out . Should I return siren and leave and see if a problem arises. Your info about chirping was invaluable . Thank you for detailed info. You may have saved me £93. I assume they will refund me :/)

 

[ABravo]

Dec if ever you are in Basingstoke let me know, I have acces to a lovely restaurant where I will set you up with a nice meal

 

[Dec]

Hold on to that new siren for now you might still need it.
My comments are based on the fact that the siren appears to be chirping as it should when locking and unlocking, however 5 seconds is not right, its too short a time for the siren to sound, it should be about 30 seconds, 5 seconds would not be much of a deterrent to a car thief.

I would test it again, perhaps tomorrow, assuming the car has had a good run and the car battery is well charged up.

These car alarms, and if yours is the original factory fitted unit, do give trouble at about 10 years of age so its wise to take note of how it will performs over the next couple of days. These alarms, when the are 10 years old do suffer when deprived of a 12v supply and this can kill them off, yours may be dieing slowly. Thanks for the offer but am way, way too over fed already.

Dec
Example

 

[ABravo]

Will hold on for a while. Battery has been charged fully but driving it to London at weekend. Think you are right and is dieing slowly. :-( seams logical. Now I have I have it, probably will change once I get it back. You're right , 5 seconds isn't much of a deterrant . Better to safe than sorry and it is for my daughter. You have been really helpful. Thank you. Once changed will let you know. She is away at uni now so no rush

 

[Dec]

Another good guide below.

Dec

https://www.youtube.com/watch?v=BzmpeK1TFfw

 

[ABravo]

Thank you every one . Siren replaced, works perfect now.

 

[Dec]

Bravo!

Dec