I used Simple Green at 40% on both sides. That brought the dirt to the surface. It did not look that bad to start with, honest. I just knew they were a bit grubby.
Once the dirt was loose I hit it both sides with my Karcher and left them to dry in the sun. They now retract like new, too.
Yep, that's right Steven. I must admit to not knowing about the dirty belts not retracting until I was told - a couple of years back.
I did the ones in the picture without removing them. I undid the lower mounting of the loop and extended the belt fully. The closed the door on it but kept it flat. My worthy assistant held the belt while I applied the cleaner and then high pressure rinse. By keeping the free end low the liquids ran away from the car. I did have to support the belt with one hand during the rinse.
Thank you M1FF...great tip! I have a set of seat belts that need a super cleaning job done to them. I will follow your instructions and see how they come out. They are red so the before and after pictures might not be so contrasting as yours.
I have cleaned belts before and they do become much more pliable after all the dirt etc. is cleaned from them. I imagine that would be a great help for retractable belts to work.