Fixed!
So I thought, nothing to lose by taking apart the automatic top element control - it didn't work anyway. The tricky thing with these is the sensor and control are permanently connected so it can't easily be removed from the stove.
As I mentioned, there were two things happening with the control: the sensor was not shutting off the heat when the pan reached temperature and the indicator light was on even if the element was turned off.
Turned out the problems were related.
I found continuity between L1 & 4 (the pilot light) when the control was turned off. This was why the light wasn't going off. I took the back off and didn't see anything obviously wrong so I moved on to trying to figure out the reason for the constant high heat.
There is a small actuator at the switch end of the thermostat line. This moves backwards and forwards with changes in temperature from the sensor in the burner. This movement mechanically opens and closes the contacts inside the switch to turn the heat off and on to maintain the temperature. I found the actuator was gummed up and stuck in its shaft, unable to move the contacts open to shut off the burner when the target setting was reached. I cleaned it up and gave it a tiny squirt of WD40 and got it moving again. The spring that pushes the contacts open when the switch is shut off was also stuck - hence why the pilot light was always on.
Once both were unstuck and free to move again, the control had to be recalibrated. This was actually the most difficult and time consuming part of the repair as the adjustment has to be very precise to make the controls work properly and it has to be adjusted in two separate spots.
Once I got the hang of the calibration I put everything back and tested it out and SUCCESS!!!
I'm really happy about this as its a really great feature and was going to be next to impossible to find a replacement.
