My Mercedes C180 alarm has caused a dead battery. How can I open the boot?

[Lacmag2]

I returned from a few days away to find my Mercedes C180 making a noise, like a faint alarm going off. I had to open the car with the key (rather than the remote) and the car battery is dead. 24hours later and the alarm noise is still going on. Where do I start? How can I even open the boot as the key won't enter boot lock.?

[rd14962]

Connect a slave battery to the alternator live terminal and an earth. Then the central locking should work. nother couple of things you could try; Check to see if the rear passenger seat will fold down giving you access to the boot and also keep trying with the key you have, try some oil on the key and give it good wriggle, it should pop open. Hope this helps.
Rupert