The one from which the spark beats is a magnet, and the thermocouple is next to or on the opposite side. The voltage is high there, but I do not remember what order. These sparkplugs are available for purchase and the replacement is simple, you just need to pull the top of the oven, and this is no longer so easy because of the seared screws fixing it to the burners. If you manage to unscrew the 8 pieces, it will go on just like a petal. The magnet is attached to the basket of the burner from the bottom there is a bolt, which must be pulled out and the tip pulled up, and then disconnect the wire from the power generator (a small box in the back of the oven inside).
Simple job. The thermocouple works on the principle that by pressing the gas tap we simultaneously push the valve core, which is inside the coil, and the thermocouple tip after heating with a flame as if it converts the heat into an electromagnetic pulse passing it to the winding of the coil. The tip cools when the flame extinguishes and the core in the valve is released. Then the core, retracting with the seal, closes the gas supply. Hence the name of the leakage gas protection. Later I'll throw in a photo of the valve because it just happens that I have Amica on the table. Greetings. I attach photos.
edit: Here you have sample links for the thermocouple and valve but you have to dismantle it because it comes with one wire and then the mass is in contact with the bowl of the burner (maybe you already have too much dirt) and two-wire, but with different connection method. You must view yours. I think, however, that if all the valves work, as you wrote above, you probably need a pad under the dial. You can also unscrew the thermocouple valve and check if the gasket sits on it. It happens that the gasket drops and stays in the gas valve.
On the third
foto A it is the marked thermocouple tip, B is a magnet. Greetings.
