Found this stuff recommended on another car forum. Bought some and tried it on my NC which has slow retracting and sometimes sticky seatbelts.
They no longer stick and now fully retract, if a little more slowly than in my other cars
I’d say give it a go, easier than washing the belts and not messy at all…
I have the same problem. Just found this on Amazon for £20 or e-Bay for £7.99 with free shipping!
I bought it from eBay, arrived within 2 days. I think there’s enough for about 5 applications at a guess
Excellent.
I have tried cleaning mine before which did help but they are sticking again so just ordered off eBay at £7’.99.
Thanks for the info.
Regards
Rob.
Just ordered some for my NC also. Had to use the right terms to find it, here’s the link encase anyone else comes across this thread: TUNAP PROFESSIONAL 104 CAR INTERIOR CARE 400ML SPRAY – MADE IN GERMANY 4002325810438 | eBay
Before you do anything just remove the belt guide from the top of the seat and see if that makes any difference to the way the belt retracts. You may also find that the metal loop on the body also slows the retraction down. It’s possible to modify the belt guide to make it run smoother and also the angle of the loop which also helps I’m sure there is a previous post about this but I can’t find it at the moment.
Just purchased some Tunap 104 and applied it to my driver’s seat belt. Much better retraction after application. Will see if this continues in future use.
Yep just sprayed my seatbelts with it today and they certainly felt smoother on retraction and quicker to roll back. Will see how they are on Friday when I use the car again .
I carried out the adjustment to the seat belt loop as per the link above and the belt still retracts fine.
Well I have to say my seatbelts are still gliding back much better after using the spray on them.
Mine too.
Tried the Lazy mod but made no difference. The passengers side is better and I noticed the seat belt guides were different. The drivers side has an additional bit in so I cut it off, made no difference.
Mx5 spares. There is a updated part . Changed mine a year a go now works fine
The modified guide helps, but a good clean works better.
Extract as much of the belt as you can and dunk it in a bucket of warm soapy water.
Clean it to within an inch of its life. Spend 10 minutes washing it. Rinse in clean water. Dry best you can with a towel. Consider washing it again.
I found the opposite 
The clean and lube gave a small improvement but modifying the guide solved the problem entirely.
Glad I found this post - have an MOT coming up soon…
Facing the same issue with my ND - tried the bucket of soap, soak and rinse - some slight improvement but still not retracting fully.
Have ordered the Tunap 104 from Ebay - now £15 - inflation!
My MOT man wasn’t bothered about the retraction issue with my previous NC or now the slight retraction issue in my present NC. As long as it works as it should do in all other respects it’s fine, never an advisory either.
Thanks for the confirmation - I had read this motestor which states that Seat belt retractor not functioning as intended would be a major defect.
Ah well - it was bugging me anyway when it flopped around - and occasionally got caught in the door jamb when shutting it … hopefully that will be resolved…
As said, the updated part from MX5Parts works a treat.
None of the other solutions worked for me
I solved this problem by buying the modified seat belt guides (that fit on top of the seats) - fitting these + cleaning made the belt retraction much much better - I think they were £30ish for the pair, but worth it.
