Faulty alarm 500SL

[gfern]

Can anyone help please my alarm has suddenly developed a mind of it's own. It goes off for no apparent reason and then resets it may stay OK for several days or it could go off twice a day or night . I don't even know where to look does anyone know where it is or can you suggest what to check for. Can it be turned off. Help please before I lose any friends I might have amongst my neighbours.

 

[justinb]

Hi,

You have my sympathy....my 500sl (129) had exactly the same problems to the point where it ran the battery flat!!

I'm still not sure what the cause is as I tried opening the door, locking it with the remote, opening, starting the ignition..all the the things you think would turn it off.

I then discovered that as I was about to disconnect the battery in a fit of pique that there is a multi-plug just next to the fuel filler cap. I heard it clicking in time to the horn and indicators so disconnected it...as if my magic, the alarm is now silent..but ineffective coz its not connected...

Not an ideal solution but it stops the embarrasing moments in car parks when everyone looks at you as if your about to knick it!!

Still trying to find the solution.

 

[gfern]

Hi Justin

Thanks for the info on turning it off. I have been searching for this solution for the last week but reluctant to just pull any wires off. There are lots of threads here on alarm problems but none that I could get any help from. I am lucky in that mine does not go off continuosly so no flat battery to date. It really is the most annoying fault but at least it doesn't immobilise the car so you can drive it away if you can live with the embarrasment, don't wear a burberry baseball cap if attempting this.

I beleieve that it goes off by sensing a voltage drop ie. when the door opens and the interior light goes on or the boot or the bonnet which has a switch operated when opening the bonnet.

I have checked all the fuses and replaced any that looked old, this did nothing. I have now turned my attention to the boot locks and the door locks. So far I have cleaned any electrical connections on the boot opening area, there is a small micro switch that operates the light in the boot. I did this yesterday a.m. and so far the alarm has not gone off. I always suspected this area because the first time it happened was when I loaded my golf clubs overnight for an early start and maybe the boot wasn't closed properly. If this doesnt work I will move through each of the door locks and if that doesn't work will pull the plug before finding a good auto electrician. Will keep you informed on any progress best of luck with solving your own problem.

Geoff

 

[justinb]

Hi Geoff,

Next step for me is to take some time to look around each of the switches adn see if they are dirty. It's alomost as if the alarm is activated when I close the doors with the remote but not not deactivated when I go to open the car. Inevitably, the alarm goes off. Initially I thought I had a problem with the central looking vacuum pump draining the battery, but since the alarm has been disconnected, it had worked fine.

Time to start checking me thinks..