Twice now, after I installed a new alarm /siren unit which I got from Mercedes dealer. the alarm has sounded while the car was parked and locked. Using the remote, I unlocked it and then locked it and the alarm stopped. I asked the serviceman at my Chrysler dealer and he told me it might be a defective door switch. Has anyone else experienced this and how did you fix it? Thank you. Mine is a 2005 coupe with 60,000 miles.

 

What was the reason you replaced the alarm? Was it going of then as well?
Some background might be handy to know.

 

alarm unit was acting funky. It went off with a weak sounding alarm sound. I opened the door manually and tried to start the car but couldn't. I disconnected the battery, reconnected and it stopped. I read on the forum from other owners that the alarm siren unit has batteries and when they start to go they leak on the printed circuit board and that makes the unit act weird. So I replaced it and my issues went away except for this occasional alarming for no apparent reason.

 

What I am getting at is did it act the same then as now except for the sound level? I am suspecting it did.
I am trying to find out if this is a new problem or a noisier old problem.
Have you looked for water in the trunk? The pump module is an integral part of the security system and if water has got into the well were the unit sits under the foam in the trunk you may find that is the problem. Look in the well under the trunk mat, water may be visible down the gap between the foam and the trunk well, use a paper towel and slide it down the crack.

 

No. The issues are different. Originally it sounded and I couldn't do anything but disconnect the battery to silence it. Now I can unlock and then lock it with the remote to silence it. Also, the unit I replaced was under the windshield wiper cowl, not in the trunk. I will check for water as you suggest though. Thank you. Btw, the unit I replaced was Mercedes part # A 219 820 32 26. It costs about $220.

 

YIKES!!!!!

You paid $220 for the siren module? It is a $100 part. Well could be a couple of things, First off have you replaced the battery? If you are still running on the white Varta battery then change it out. They make everything freak out! These cars are very sensitive to the electrical voltage.

The Issue 180 brought up should be first on your list after Battery and Siren, both of which you have done. I have also heard recently of a lot of Ground cables going bad. they are getting corroded on cars in wetter climates. This can cause a variety of issues including security system misfires. I am fairly certain it is not a door switch, and since a Chrysler dealer mentioned it, then it probably isn't. ( stop taking your car to Chrysler dealers, your car is not a Chrysler.)

 

wow easy does it !!! The mans asking for help !!! Just remember to shop around when needing parts & try & stay away fro dealers Chrysler or Mercedes !! Always ask here where people find the best price on parts ok !!!