My 04 crossfire coupe just suddenly starting having the alarm go off. Using the key fob or door locks does not stop it. Any advise what's causing this and how can I stop it.

 

you want believe me but replace your Batt. and your problem solved. jim

 

+1, yup change your battery. car does funny things with a weak battery.

 

Three problems that I have heard of:
If it sounds normal and the battery is the original white Varta or old it is probably the battery.
If it sounds a little off like it is a "dying cricket" then it may be the alarm siren - only way to keep it quiet is to leave it unlocked until you replace it. Buy from Mercedes not Chrysler - #'s on the forum.
Also a problem with water in the trunk getting the locking module wet. Instructions available without removing the foam.
Do a search and you should be able to get the info you need on the forum. A good start is: https://www.crossfireforum.org/forum...ht=alarm+siren

 

To add to what Ron has already posted there is another issue. The siren itself has an internal battery which eventually dies then leaks over the siren circuit board causing the same issues. Either replace the whole siren module or take it apart and replace the batteries. I did this a few months ago and is still working great. Total cost about £12 and a few hours work. There is a thread somewhere about it which I contributed to so have a search ( can't do links whilst im using the mobile to post).
Matt

 

I just started having the same problem with my alarm going off at random, today even the key fob would not shut it off and I know it was not the batteries in the fob because they were just replaced. I realize that my car is 9 years old and cannot expect things to last forever, but would like to know who is the best to go through? Chrysler or Mercedes for parts? Also were is the security alarm located so I can check the battery in the module?
He He I am just full of questions today but I love my car and want to get her back in her girdle so to speek.

 

Always buy the Mercedes part, Chrysler just marks them up a lot.
If you want to see the siren it can be found under the cowl in front of the windshield. You'll have to remove the wiper arms, some screws and some fasteners. Voila!
This PDF file shows what is under the cowl and you can see a picture of the siren in it.