Mercedes-Benz GLC Owner's Manual page 312

Problems with trailer towing
Problem
The displaced ball cou-
pling does not reach
the securely locked
position.
Unlocking using the
button in the tailgate:
The ball coupling does
not swivel, even
though:
the vehicle is station-
R
ary
no trailer cable is
R
connected
the button was
R
briefly pulled.
Possible causes/consequences and M M Solutions
The indicator lamp in the button flashes.
R
The Trailer coupling Check lock Trailer coupling Check lock
R
multifunction display.
Initiate a new swivelling procedure.
X
If the ball coupling does not reach the safely engaged position as
a result:
Start the engine
X
or
Pull and hold the button during the whole swivelling procedure.
X
If the unlocked ball coupling does not reach the safely engaged
position even after several attempts:
Make sure that there is sufficient ground clearance before con-
X
tinuing the journey.
Consult a qualified specialist workshop.
X
As long as the display message
is shown in the multifunction display, no trailer should be attached.
The on-board voltage is too low.
Start the engine.
X
If the ball coupling still does not unlock:
Consult a qualified specialist workshop.
X
Towing a trailer
message appears in the
Trailer coupling Trailer coupling Check
309
Check lock lock
Z