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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53901
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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I have a 2007 Mercedes c230 and 1 day my alarm went off

Customer Question

Hello I have a 2007 Mercedes c230 and 1 day my alarm went off for no reason and would only go off once I put the key in the ignition. An hour later, the alarm kept going off, I disconnected the battery and the alarm was still going off. So I went to buy a new battery for the key fob and it only allowed me to lock and unlock the door 1 time. now I can only use the smart key to start the car, nothing else
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, it sounds like your alarm siren has gone bad and it may have blown the fuse. Check fuse #8 in the trunk fuse box and see if it is blown. If it is you can replace the fuse and get the remote working again but your siren may still go off randomly. You will probably need to replace the siren to repair the problem. It's also possible that the battery in the remote is not making good contact.

Let me know what you find out.


Customer: replied 1 year ago.
How do I know which fuse is fuse 8. .also the 3rd relay or fuse is missing from the left side of the fuse box, could that be it
Expert:  Marty replied 1 year ago.

Click on the fuse box diagram below. It won't be a missing relay problem.