That stuff all looks nearly brand new!
Don’t adjust the height of the burner or valve! That’s not how the flow rates are adjusted. The cold oil depth is only needed to get the burner lit. The maximum cold oil depth is set to ensure that if the oil level reaches the safety trip level in the control valve that the oil won’t flood over the top of the burner.If I recall, AGAs were set up to run at full temperature 24/7.
But those oil control boxes do offer a degree of controllability so, you could try altering the knob to have it idle. Overnight, say. If you find "minimum" is still too hot, you can raise the burner a bit or lower the control box, to lower the oil level. Therell be a minimum you can get away with though, the burner needs to be hot enough to properly vaporise.
Best hope no one has mucked about with the little control alteration screws on that oil control box though. Resetting them either involves careful measurement (assuming you can find the setup spec) or very time consuming iterations.
That stuff all looks nearly brand new!
It’s s long time since I built an aga so can’t remember but if you look carefully at the castings you can probably work out the route it would take to the oven. Dependent on age it may have been designed so the stat can be replaced without taking the top off.I set the temp by the thermometer on the AGA, to keep the mercury on the black line. I had to set up the heights of the vaporiser and the BM float valve, and I do all my own servicing. a new valve, controller and thermostat would be well over £350, I could by second hand, just not sure where the stat lives.