nissan sentra 96 wiper going only half way in timer mode

My Nissan sentra 96 wipers stops halfway when switching the control on timing wiping. In fast and slow speeds works fine. It is jus the relay mode that has this problem of going forward half way and stops right in the middle of the windshield. any suggestions? There is any relay timing that I have to replace? the wiper motor looks good and no weird sound makes. Thank you,