Alarm Problems - E240 'X' Reg Est (2000)

[Wattoh]

Help please:

I have a 2000 ‘X’ Reg E240 (2.6) Estate. A few days ago, my wife unloaded all the children, but did not close the back door properly. It was latched, but not totally shut. It then rained heavily and although the children’s seat and the protective mat it was sitting on caught most of the rain, the trim between the seat the door got very wet.

Then that evening we had alarm problems: going off that night a couple of times (siren and flashing lights). I investigated and re-set before going to bed. It went off once overnight.

Since then, after differing periods of time from 5 mins to maybe an hour, the indicator lights flash madly but there is now no sound at all. Sometimes the interior lights in the back half of the car also come on at the same time (ie NOT those over the front seats), and sometimes those same lights come on only when I press the unlock button on the key.

I have also noticed that the light in the ‘Tow Protection/Sensor’ switch on the dash flickers from time to time (which it did not used to).

I have done the following (none of which have worked):

1. I have checked for insects which might set off the alarm (but why no more sound??).
2. I have checked all windows are shut tight and the doors and boot are shut tight. There is no other water ingress that I can see.
3. I have taken the car for a spin with a hope that it might ‘reset’ anything which might be awry.
4. I have tried pressing the ‘Tow Protection/Sensor’ switch up and down.

Any ideas most welcome! Could the dashboard switch be to blame? Do the sensors need attention? There is nothing hanging inside the car (eg furry dice!!). Car starts normally.

Thanks!

 

[Blobcat]

I'm thinking that the rear door light switch has water inside it. If you can get it out an clean it that would be the best. If not a quick spray with Water Displacement No. 40 is a quick fix

 

[Wattoh]

Thank you! I'll try that.

 

[Wattoh]

I'm still at office & unable yet to try suggested remedy. My wife tells me the siren is now going constantly but not the lights!

Is it easy to disconnect the siren under the bonnet? What am I looking for? It's a W210 estate.

Thanks!

 

[merc-tech]

Look under the rear seat behind the driver - the pse pump is situated by the battery and these fill up with water causing all sorts of probs

 

[Wattoh]

Thanks. I got the seat up yesterday evening. Siren going constantly the instant the doors are locked. The black webbing around the wires in that 'well area' is still damp.

I did wonder what the other black thing was next to the battery. Er, what's a pse pump...?! And what does it do? Can it just 'dry out' and work?

Today, the local non-dealer Merc specialist first thought (on the phone) that I needed a new door lock (apparently where the sensor is), but when they hooked it up to the computer, 'the computer says' the siren needs replacing. They could not see the connection between the rain ingress off-side rear, and the problem with the siren near-side front. Computer raised no more problems but said there is a 99% chance it will sort everything.

Any comments/pointers? Thanks!