My pool cleaner does not climb up the wall.

by Jan Rohar
(Slovakia)

My pool cleaner Dolphin Maytronics Diagnostics 2001 does not climb up the wall, but once I help him to pull up the front part a bit, he has enough vacuum power to stay stuck to the wall and drive up to the water surface.
I have noticed, that after approaching the wall he does not get any impuls - I think that turbine should revert turning direction for a moment and push the nose of the cleaner a bit up - in order to start climbing the wall.
Where to focus me in order to find out why the cleaner does not start climbing?
All the parts are carefully cleaned, repeatedly checked and all look in perfect condition.

Jan R