Alarm rf transmitter not working and no alarm siren

[F355]

Dear All

I am new to this website, and in fact new to the whole forum resource that is available on the Internet.

I have purchased a merc clk (2004), and after a bad experience with a "merc specialist" I would rather begin to learn and understand my car myself, and hopefully try to be a knowledge source for others in the future.

I would be very grateful if anybody can help diagnose my problem.

Symptoms:
- one minute my key fob was working fine. And the other it stopped working from a distance.
- I.e. the key fob works fine, however only when I point it to the sensor on the driver side door panel, and from close range.
- it seems the rf transmitter for the key fob is not working.
- when I slide the key out of the remote fob, and use it to manually open the door, the car alarm is set off. HOWEVER there is no alarm siren. Only the indicators all start to flash.
- fuse number 8 (which is located in the boot and related to the alarm system) has short circuited. I have tried changing the fuse twice, but no success as the new fuses immediately short also.

Does anybody know what the problem is?
And whether I can attempt to repair the problem myself?

Any help would be greatly appreciated.

Thanks for reading.

 

[F355]

Dear All

I am new to this website, and in fact new to the whole forum resource that is available on the Internet.

I have purchased a merc clk (2004), and after a bad experience with a "merc specialist" I would rather begin to learn and understand my car myself, and hopefully try to be a knowledge source for others in the future.

I would be very grateful if anybody can help diagnose my problem.

Symptoms:
- one minute my key fob was working fine. And the other it stopped working from a distance.
- I.e. Although i am still able to lock/unlock the car with the fob, only however when I point it to the sensor on the driver side door panel, and from close range.
- it seems that the rf transmitter for the key fob is not working. And therefore the fob is not functional from a distance.
- when I slide the key out of the remote fob, and use it to manually open the door, the car alarm is set off. HOWEVER there is no alarm siren. Only the indicators begin to flash.
- fuse number 8 (which is located in the boot and related to the alarm system) has short circuited. I have tried changing the fuse twice, but no success as the new fuses immediately short also.

Does anybody know what the problem is?
And whether I can attempt to repair the problem myself?

Any help would be greatly appreciated.

Thanks for reading.

 

[Dec]

When you lock the car with the remote you also arm the alarm.
If you then unlock the door or the boot with the metal key blade then the alarm will be triggered when you open the door or boot, that is normal, the metal key is for emergency enter into the car, it doesn’t disarm the alarm.

In your case, the alarm siren, which contains the brains of the alarm system is defective and needs to be replaced with a new one from an MB dealer, about £90 and easy to fit. The defective siren is probably what is blowing the fuse, unplugging the siren should stop the fuse blowing…I think?

The other issue may be to do with the receiver for the RF rather than the remote fob, don’t know too much about this but the receiver is at the back window and uses the top wires in the back window as the antenna, is the radio reception good or bad?


Also change the batteries inside the remote fob.

Dec

 

[F355]

Hi Dec, and many thanks for your input.

I have replied to your queries below:

- I too, at first, suspected the rf transmitter. And after some reading learnt about the rf antenna amplifier that you spoke about. I can confirm however that the radio reception is as normal with no problems.

- I don't know how to disconnect the siren (in order to stop the fuse blowing). Are you able to describe this to me quite easily? Of course once I can disconnect it, I presume changing it will be pretty self explanatory.

Thanks again mate.

 

[Dec]

Below link is just general information but may be of some help.
See… Welcome to the C209 CLK-Class!
Then Click Electrical then Click Central Locking.
I’m not to sure about the RF problem, others might be of some assistance as to how to proceed to fix the problem.



Re Alarm, Click Electrical then Anti-Theft Alarm (ATA) in above link.

When you locate the siren, unbolt it and then unplug it, note it might go off when you unplug it, it’s unlikely that it will as it didn’t sound before when you unlocked the car.
You can drive and lock the car as normal with it unplugged, just cover the plug with tape to keep it clean/dry as the plug will be live.

I don’t know where the siren is on your car but it may be located behind the wheel arch, example of a W203 here… http://www.mbclub.co.uk/forums/electronics/86238-indicators-fast-flashing-no-apparent-reason.html
Let us know how you get on.

Dec

 

[Railwayman]

Hi

Have just repaired my 2003 W209 with same problem (fuse 8 7.5 amp), replaced the alarm siren which is located in the front near side wheel arch behind the mud cover (rear). It sits in a metal bracket bolted to the underfloor. Cost was £102 from dealer and took me about 1 hour to do.
Hope this helps.

 

[1945wickedred]

Hi my problem is with the hazards flashing if I do not lock the car with the fob.Siren was removed some time ago because of the unbearable noise,it must have been on the way out.So if I fit a new siren will the alarm system go back to normal if there is such a thing with a MB.

 

[Dec]

It all depends on the type of remote fob you have and what year the car is?

Dec