Mercedes-Benz M-Class 2012 Owners Manual - Manual (Page 221)

Otherwise, you and others could be injured by
the ball coupling being thrown around if you:
R brake sharply
R change direction suddenly
R are involved in an accident
X Open the stowage well under the cargo
compartment floor.
X Remove the protective cap from the ball
coupling recess.
X Press the protective cap into the ball
coupling recess until it engages.
X
Make sure that the protective cap is firmly
in place.
X Store the ball coupling in the ball coupling
recess with the bolt and spring cotter
inserted.
Trailer power supply
The trailer socket of your vehicle is equipped
at the factory with a permanent power supply.
The permanent power supply is supplied via
trailer socket pin 4.
! You can connect accessories with a
maximum power consumption of 240 W to
the permanent power supply.
You must not charge a trailer battery using
the power supply.
The trailer's permanent power supply is
switched off in the event of low vehicle supply
voltage and after six hours at the latest.
You can obtain further information about
installing the trailer electrics from a qualified
specialist workshop, e.g. an authorized
Mercedes-Benz Center.
Trailer towing
219
Driving
and
parking
Z