I have a '99 ML430 and I'm having a problem with the alarm. When I activate the alarm the doors lock and the lights come on like normal. But then when I open it with the spare key the alarm doesnt go off, only the lights flash. Does anyone know whats the reason behind this?

The Mercedes dealer told me I had to replace the horn but when I press the horn it sounds the same as it did when I first bought the car.

Could this just be a fuse or something?

Thanks.

 

Anybody?

 

Alarm horn is not the same horn as you operate from your steering wheel. So how did you test it? Alarm horn is up by your brake fluid reservoir. You could have bad relay or wire connection. Take the correct horn off and connect it to the battery to hear if it's good, just don't get scared!