Auto-Fill not working

[TouTou]

Please advise if I have posted this in the wrong section. Wasn't sure where it should be posted.

We have an in-ground pool with an auto-fill system. This year it is not working correctly. We have replaced the floater and the valve, but we still have the same problem. Water continuously flows into the pool. We initially thought it was the floater and/or valve, but after replacing them, we realize that was not the problem. A bit of internet research came up with the possibility that the sensor is bad (electrical circuit for sensor gone bad). From what I've read, when the sensor is bad, it obviously does not read what the floater is telling it and it stays in an 'on' position, allowing water to continuously flow into the pool. Are sensor issues repaired by electricians or would this be a task for a pool service repair company?

We have turned off the water source to the pool, but we need to know what to do next.

Any ideas of things that could cause this? Am I on the right track with the sensor issue or do you folks think it could be something else?

Many thanks to anyone with any ideas.