New to MB here! I have a C230 with a dead battery (trunk), mechanical
key does not operate in the trunk slot. Any ideas on how to open it
so I can recharge battery?

 

There is a power point under the hood which you can connect another battery or charger to,this will allow you to open the trunk lock using your remote or the unlock switch inside the car. The power point,+ve, is in a black plastic box about 4"x2" located at the front of the ecu compartment to the rear of the engine bay, connect your -ve to any suitable ground point on the engine.
Hope this helps ,Geo.

 

what shandy2550 says is true, but if you can't get the hood open (if your doors are locked), keep trying that mechanical key in the trunk. It's a b*tch to turn, but it does open the trunk.

 

Hey guys, thanks for the tips!
My 16 year old (son) injected 4 to 5 squirts of WD-40 into the slot and
finally got the key to turn, great advice.
I will also try to locate the power point, another great tip.