Random Alarm Incidents with S210

[Nastynick]

Hi.

My '99 S210's alarm keeps going off at random intervals.

Has anyone else had this problem? Its just another electrical gremlin to add to the list.

Might have to get rid.......:-(

 

[Dieselman]

It is likely to be either the interior sensors being tripped or the alarm battery gone flat.

 

[Nastynick]

Where would I find the alarm battery?

 

[Dieselman]

In the alarm siren.

 

[ringway]

Could also be the PSE.

Check under the O/S rear seat where the battery is. There's a foam boot that houses the PSE unit and if the foam is damp, the circuit board in the unit will be playing up. If there is dampness (or indeed a puddle on the floor) the drain under the wiper assy needs clearing.

 

[richard]

Its just about spider time, so there could be spider in the car ! (yes, its quite common)

R

 

[Nastynick]

There IS a massive, fat bodied spider that had spun a web twice on the trot at night. Not managed to trap it yet so have turned off interior ultrasonics in the meantime.

 

[Druk]

My 211 started doing exactly this same thing last year. Corroded PCB in the siren. New siren fitted and cured. Not hellish expensive iirc. Siren located under O/S wheelarch cover on 211. Fairly common fault apparently.

 

[simonjamesturne]

I have the exact same fault on my W211. Random alarms and hazard light flashing. All can be cancelled by repeating the locking sequence a few times. I think I'll attempt a repair as it seems that the fault is well known and comes down to a PCB mounted Varta battery which corrodes its terminals. The battery is a Maplin part number at less then £10. The same siren unit appears to be on most Mercedes models. Fortunately the fault doesn't activate the immobiliser so apart from the inconvenience it can be lived with.

 

[grumpyoldgit]

Deter spiders by placing a few conkers in the car. They are about now.
I always thought it was an old wives tale but it seems to work in the house.

 

[Druk]

I have the exact same fault on my W211. Random alarms and hazard light flashing. All can be cancelled by repeating the locking sequence a few times. I think I'll attempt a repair as it seems that the fault is well known and comes down to a PCB mounted Varta battery which corrodes its terminals. The battery is a Maplin part number at less then £10. The same siren unit appears to be on most Mercedes models. Fortunately the fault doesn't activate the immobiliser so apart from the inconvenience it can be lived with.

I took my duff one apart for a look. It is the battery leaking that causes it but by the time the fault appears the PCB had been damaged. Not worth the effort.

 

[simonjamesturne]

Just took mine apart too. You were right the damage to the PCB is too great to make a repair worthwhile, still the car runs alright without it so I'll source one in due course. It was a bit of hassle getting to it though, they couldn't of hid it any better.

 

[simonjamesturne]

Finally fitted a new alarm siren. The replacement part is a little different then the old one but still fits. Interestingly the new siren has enabled an "Alarm Arming" bleeping which wasn't originally available. An upgrade, I guess?

 

[KillerHERTZ]

Finally fitted a new alarm siren. The replacement part is a little different then the old one but still fits. Interestingly the new siren has enabled an "Alarm Arming" bleeping which wasn't originally available. An upgrade, I guess?

Mine has done the same, its meant to be the 'Netherlands' mode, normally enabled through STAR.

 

[martyp87]

Mine has started doing this too.

Sometimes its absolutely perfect other times, about 5 secs after locking the car the alarm will activate and I need to unlock the car, hit the lock button on the dash and lock the driver door with the key. Complete pain in the backside.

 

[pedders911]

I have just been round the same cycle. 2003 E class Estate false alarming sometimes with siren, sometimes without (flashing indicators only...). Changed siren (yes battery corroded the circuit board) and all is well. Local MB garage (Bristol) reckon they do six a month, usually at the ten year point - the fact that they had three in stock spoke volumes - (£85+VAT) :-( New unit smaller and with a male thread, rather than female, but plug the same and easy to install. Only need to undo the top O/S wheel guard (I found it easier to take the wheel off) bending it, to gain access to the unit: mounted high on inner wing on threaded studs by long 8mm captive nuts - needing a deep draw 8mm socket.

 

[A-AvantGarde]

I have just been round the same cycle. 2003 E class Estate false alarming sometimes with siren, sometimes without (flashing indicators only...). Changed siren (yes battery corroded the circuit board) and all is well. Local MB garage (Bristol) reckon they do six a month, usually at the ten year point - the fact that they had three in stock spoke volumes - (£85+VAT) :-( New unit smaller and with a male thread, rather than female, but plug the same and easy to install. Only need to undo the top O/S wheel guard (I found it easier to take the wheel off) bending it, to gain access to the unit: mounted high on inner wing on threaded studs by long 8mm captive nuts - needing a deep draw 8mm socket.

Do you happen to have the part number handy at all?

 

[pedders911]

Yep, though I had to go to the salvage for the box, as I wasn't about to strip the wheel arch cover again! its A219 820 32 26