Aqua 3000 shower fitted new 3 months doesnt provide water at required temp?

In mid power setting with 10 temp dial setting (max) we can get warm water, on high setting with temp dial between 6 and 10 we get scalding water, any lower than 6 and the power light cuts out and the water runs cold

Ideally we require the water to run hot with a high power setting

Is this possible?