Mercedes-Benz CLK-Class Owner's Manual page 323

Practical advice
Troubleshooting
Seat belt
Problem
The seat belt extender does not slide back. The seat belt extender is defective.
320
Possible cause/consequence Suggested solutions
Push the seat belt extender back with
force.
Have the seat belt extender checked
at a qualified specialist workshop, e.g.
a Mercedes-Benz Service Centre.
If you are unable to push the seat belt
extender back:
Do not drive any further and inform a
qualified specialist workshop, e.g. a
Mercedes-Benz Service Centre.
G
There is otherwise a risk of injury.