Thetford Agua-Magic Problem: Follow Up

Just thought I would post a follow up on this problem in case others run into it. When I pulled the head and examined it on the bench, I found the (plastic) ball drive arm was warped from the long term pressure from the spring. This was causing the linkage arm from the drive arm to the water valve to scrape on the bowl casing and not allowing the link to slide in the slot in the drive arm. That held off water being introduced to the bowl until the ball assembly reached an open position and forced the link to open the water valve. Thus water could not be added to the bowl with the ball closed.

Replaced the water valve, ball drive arm, ball and seal, and base seal since it was a perfect time to easily get at everything. Working perfectly now.