White knight 44AW temperature settings not right?

Hi. My white knight 44AW tumble dryer settings don't seem to be working right. When on high heat setting the clothes are red hot and almost to hot to touch; far hotter than they used to get...and when I put the dryer on low setting the heat is virtually non existent, again no where like the temperature it used to reach when working on the low setting. Why is the high heat getting to hot and the low heat to low; the settings never used to be like this. Please can you tell me what is wrong with it and how I can sort it. Thank you