Rear Seatbelts occasionally lock tight and won't roll out (2003 ML 270)

[Axcontrols]

Somebody sits in the back. Seatbelt rolls out and can be fastened ok but occasionally, during the journey, one or other of the belts locks tight and person can't lean forward. Only way to release is to roll the belt all the way back in again.

Is this something in the belt tensioner going into accident mode. Or maybe something to do with the seat base/backrest/frame of the seat being properly fixed in position - for example after lying the seat down flat and lifting it back up again.

It's not all the time but it's annoying.

Cheers
Ian

 

[Frontstep]

Have they been off ?
If they don't go back straight it might be the issue.

 

[Axcontrols]

Sorry. What do you mean "Been Off"?

Do you mean have the belts been removed from the car? No. Never. Seats or belts have never been dismantled.

They always retract smoothly. Not twisted or frayed or anything.