I wouldn't jump to the controller just yet. Is an expensive part. I would check the others first. You'll have to get in there, and find your defrost heater. Disconnect both sides of if, and check continuity across it. If that is there, everything i have found on this model says it will most likely be the temp sensor. Now, it COULD be that your evap fan has stopped working. You'll want to double check and makemsure the fan runs.
As for turning the water off and.setting the ac to 75, no. That had nothing to do with this and is just a coincidence. Those two things will not affect the operation of the fridge. Unless you set the temp much higher. But you didn't so you should be fine.