3900 cleaner that was a few months old not moving, plenty of water getting to and coming out the tail end.
I had this problem and fixed it after a week of trying different things...I could not find any reference to this issue on the internet. The issue ended up being debris in the small jet that shoots water on the paddle wheel to make the unit move. It was clogged and after i got it moving, one of the water jets got clogged causing it to run sideways and spin. We have a lot of leaves in our backyard so this time of year we get a lot of them in the pool. This created a major headache for me until I tracked it down...hope this helps other...real easy to fix, three screes on bottom take the cover off, then three more to take the water flow section off..The back silver grill comes off with this part.