Fixing a later GE sense a temp burner
That is the correct sensor that you found on eBay, sensor is the most likely thing but you need to test just disconnect the sensor at the control and check for about 17 1/2 ohms resistance, you can also do a quick test and put a jumper across the sensor terminals If you do that and the transformer and the responder good the burner will heat it high, but will not regulate it all. It’s dangerous to leave it that way because the burner gets very hot. It’s a high speed burner.
It could also be a bad control transformer or the responder itself.
If you don’t wanna go into the cost of replacing the expensive sensor, you can just install another infinite switch and you’ll still have the three size element and griddle settings, but you’ll just have to regulate the heat like you do with the other three burners.
As GE started to phase out the automatic burners, the last products to have them were early 80s Americana range and this cooktop, they had already discontinued them on the regular 30 inch ranges, GE also had them on the 40 inch top-of-the-line range until they stopped making 40 inch ranges around 84.
John L