Detachable tow bar problem

I've never seen a Witter bar in the metal ..... is it perhaps lack of lubrication on the receiver part.

Witter have confirmed that the detachable bit is OK, so presumably the problem lies with the static part. I'd suggest a liberal spraying of something like chain spray (it's sticky & doesn't wash off as easily) into where the detachable bit goes in, & fit & remove the bar several times. When it all works as it should, give the end of detachable bit (NOT the ball 😉) a wipe with grease from time to time.

have you been putting back the cover when not using the neck and dirt trapped inside receiver. I had this once on mine but it was because I didn't shove it up high enough as the weight made it slip down a little just as I was clicking it in.

Louise

Do not, as advised, use oil or grease in the receiving chamber. From what you describe the problem has nothing to do with that.

I had the same problem as you describe last year. The blue release knob is fouled with grime from use. This causes your problem of not being able to turn it through 180° therefore it fails to lock open (green). I suggest you let your fitter carry out this operation as follows. If you look at the blue knob you have the locking keyhole. To the side of that is a Witter logo on a reddish coloured plastic cover. You need to get a fine pointed tool and insert it to remove this cover. It will leave a small mark but it can't be helped. Behind this cover is a screw and spring the keeps the knob in place. This needs taking apart carefully to get at the inside which is where the dirt will be. Give everything a good clean (no oil) scraping away the dirt and put it back together, finally replacing the small plastic cover. If you are capable you may try doing it yourself. If not and the towbar is still under warranty then ask you fitter to do it.

Mine's worked perfectly ever since it was cleaned.

Interesting information, from it I take on board that leaving it in place longer than needed simply invites more opportunity to get grime in there. Maybe a more general observation on use of detachable hooks?

Have a look at Youtube: lots of detachable instructions and advice.

My present and last detachable were well lubricated from new, but needed cleaning and regreasing each year. What do the instructions recommend.?

Just seems like another job to do plus you lose the advantage that a fixed one keeps careless parkers at a respectful distance.

With modern crash protection that "advantage" is questionable, the tow bar places the impact forces that come courtesy of "careless parkers"  right where it can hurt your vehicle.

At least with soft bumpers there is the chance they can on occasion "heal".

When we had our detachable witter fitted we were told to give the receiver a good spray with wd40 each spring 

didnt bother first year and started to get problems as you describe 

went back to fitter, he took one look, shook his head and muttered something under his breath along the lines of “ when will people listen to me”. I fairness that’s the edited highlights of the conversation and a lot cleaner than he used 

I do this and use an old toothbrush to give the inside a bit of a scrub then another spray, you’ll be surprised how much muc comes out after a winters use