2002 Mercedes-benz C240

Repair Help Mercedes-Benz
1

A cpl days ago I got out of my car and hit the key fob to lock the doors and about 5 minutes later I noticed my fog lights on the front were blinking. I hit the fob again and they shut off for about 25-30 seconds and then started blinking again. As far as I know, they never stop. I have been using the inside button to lock my doors (leaving the drivers door unlocked by default) and I don’t seem to have the problem. I can’t afford to leave my car unlocked everywhere I go though. I have narrowed it down to the alarm siren (or i should say its batteries). This part seems to be something that can’t even be purchased through ebay or anywhere else that usually has OEM parts at a MUCH lower cost, but not this one it seems to be between $150 - $300 depending on where. My question is… If I remove the siren and don’t replace it right away, will the fact the faulty part is unplugged make the fog lights stop blinking after I lock the car with my key fob? And if it WILL stop the blinking until I can replace it, will it show a malfunction on my center dash computer, because I really don’t want to have to constantly get a malfunction display. My email address is: [email removed] phone: (812)453-1818 Please reply back to me as soon as possible since this IS my daily driver and I DEFINITELY do not like the fact I have to leave my car unlocked.

Thanks in advance,

TJ Bieber

Evansville, Indiana

2

Removing the siren will not solve the issue. The siren and blinking lights are both part of the car’s security system, designed to alert the user. Even if you disconnect the siren, the alarm system itself will still be active, and the problem you’re experiencing, like the fog lights blinking or doors not locking properly, will likely continue.

There can be several reasons why this is happening, depending on the specific fault within the alarm system. In many cases, when the alarm is active, it can also prevent the car from starting. However, since you’re able to start your car with your key, it’s likely that pressing “unlock” is temporarily disabling the alarm.

The issue could be caused by a faulty door lock, a malfunctioning alarm module, or a key fob that needs reprogramming. To reset the car alarm on a Mercedes C240, try pressing and holding both the lock and unlock buttons on the key fob simultaneously for 6-7 seconds. This may switch the setting to unlock only the driver’s door. To revert it back to unlocking all doors, repeat the process.

As another troubleshooting step, disconnect the negative terminal of the 12V battery, wait about 30 minutes, then reconnect it. If none of these steps resolve the issue, it may require reprogramming the key fob or further diagnostic work by a qualified technician.