'95 C200 - ALARM PROBLEMS!!! HELP!!!

[bc2000]

Hi Guys,
I've read every alarm posting on the forum, and still can't seem to find why my bl@@dy alarm keeps going off!!

Firstly I have a Dec 1995 C220D (Non-Turbo Diesel version) with (I think) the factory fit alarm \ immobilisor, with the red and green lights on the interior mirror and door handle.

For the past few weeks, I seem to set the alarm using the infra-red fob only for it to sound about 2 minutes later...!

I've checked the ultrasonics by taping over them (as advised by MB), I've changed the vacuum pump in the boot (incase it was leaking), Changed the batteries in the fob and looked for any light sequences that may point me in the right direction...

The Weird bit!!

I've noticed that the interior light stays on when locking the car and no longer dims out... so maybe a faulty light I hear??

Well...No. If I go around the car opening and closing the doors it stays on...until I open and close the PASSENGER SIDE, REAR DOOR! As soon as the passenger side rear door is opened and closed the light goes out.

BUT, If I enable the alarm after closing this door...It still goes off!
I initially wondered if the door pin on this door was corroded...but there is no door pin. Apparently they are all electronic, but I'm told are unlikely to go wrong.

I've also been advised that the relay that runs the dimmer for the interior light could be at fault? But I don't even know where to find this relay...

Please, Please, PLEASE can someone help me here?? I've racked by brains trying to sort this thing! :cry:

I know, I know a trip the the local M£RC garage is an option, but they've told me it won't be cheap!!

Any help appreciated!!

BC2000

 

[jaymanek]

You could go round in circles, these alarms werent the best - try turning it off with the key you should have got with the car. If that works then id take out the old alarm and put it a new one for a couple of hundred quid.

jay

 

[piestore]

alarm

if the light stays on this is setting the alarm off

find the cause, Usually faulty door pin switch, occasianally OCP (interior Light) or over head control panel

 

[42636]

hello bc200,

Its funny is this but my wifes car had a similar problem (polo). If you say the interior light has suddenly started staying on longer than normal I would say that is what is setting the alarm off. As I understand alarms they go through a check sequence (15-20 secs) to see what current draw there is and monitor this (door opens, light comes on alarm goes off). If your light does eventually go off after the 15-20 secs the alarm detects this and goes off. On my wifes polo the boot light stayed on, went off, came back on etc so it took some sussing because I could not see it (in the boot). It turned out to be moisture in the microswitch on the boot handle which was alternating between working correctly and lighting up the boot some time later and setting off the alarm. Because the lock was a pig to get to I just disconnected it all (the thieves in my area do the glass anyway) so the interior sensor would take over. For the time being I would disconnect the interior light bulb in your car then when you have more time trace the switch/delay mechanism back. I bet you a steak dinner thats the problem!

 

[grasmere]

another stab for you is to try resetting the alarm key fobs as detailed in the manual. Just a guess in case the alrm is out of sync in some way

Ian

 

[colinwilliams]

Ive has simliar prob on another car.

I was told to change the battery in the key fob

I think that the light is the root of this though .
cant help with sorting your light out ..

I turned mine off altogetehr as it was not being used enough and draining the battery.

couple of weeks later lost this littel brass key that does this so cant switch on again if i wanted to .

Ho hum

 

[Messa]

BC2000, this is uncanny!

I came on here as I have exactly the same problem, mine is with a C250TD '99.

I can set the alarm, count the 30 seconds or so and the alarm will go off. I can then turn it off, reset and it will stay on forever and a day without sounding. I have noticed on occasions the back interior light will be on when it has sounded, obviously connected, but it also does it without a light showing. I have physically removed all the door light switches ( the alarm works on a 'normally open' system so removing switches acts as if doors are shut anyway) and tried the alarm then, it still does it.

I have turned off the interior lights on door open function, it still does it.

I would say it happens about 3/5 times of setting alarm.

Strange things i noted..... if I wait 30 seconds before setting, I usually get away with it, and also, the alarm never goes off randomly ie if it does not go off 30 sec-1min after setting, it will not go off at all.

This last point makes me belive it is a timer of some sort, as if it was water/faulty switches etc it would happen at any time, not just after setting.


Anyone any ideas please as this is sooooo frustrating?

thanks,

Neil