Small Electric cooker on Range does not reach...

Question

We have (i believe) a model MXGC96GGI/CV Dual Fuel cooker of the Curva range. The problem is the orange light is always on. When the small oven is used, even on full, the cooker doesn't reach full temp. I feel sure that this is a thermostat problem, but how do I access it to change it? and where can i obtain one? please help.
Regards