Mercedes-Benz CLK-Class Owner's Manual page 267

Operation
Trailer towing
Trailer with 7-pin connector
If your trailer has a 7-pin connector, you
can connect it using an adapter cable.
The adapter cable can be obtained at a
qualified specialist workshop, e.g. at a
Mercedes-Benz Service Centre.
P 31.10-2456-31
1 Lug
2 Groove
264
Fitting an adapter cable
Lift up the cover.
Insert the connector with lug 1 into
groove 2 and turn it clockwise to the
stop.
Allow the cover to engage.
Secure the adapter cable to the trailer
using cable ties.
Permanent current
Your vehicle has been designed to provide
a permanent current connection. If you
need a permanent current supply to the
trailer, have the necessary fuse inserted at
a qualified specialist workshop, e.g. at a
Mercedes-Benz Service Centre.
i
Remove the fuse if you no longer require a
permanent current connection.