Only comes on at 1/3 and fills for a set time then will error out if not full. If the level is a "low" 1/3 it will time out and need to be reset for the next time. If it is a "high" 1/3 then it will fill to full and stay in AUTO.
Syphoning issue:
I had the service guys at Tampa Show extend my overflow tubing to create a loop. The tank has a vacuum break that has to pull open on a vacuum and without the loop not enough vacuum is created. What I didn't understand is why there is a syphon when the overflow tube doesn't go into the tank! Whatever the reason the longer loop works.