I would first check the voltages at the water inlet valve solenoids. When set for cold water and filling, you should have 120vac across the cold water solenoid connector. The ATC will cycle these solenoids on/off to turn the hot/cold water valves on/off depending on temp settings. You should be able to determine if the problem is the ATC or the valves. I can help further if you post a clear photo of the wiring diagram and timer chart that should be on the upper left side of the inside of the back panel near the top. You will need to remove the cabinet to get to the water inlet valves anyway.