white knight dryer blowing cold air?

I have a white knight dryer that is only blowing cold I have tried to reset it using the red button on the back but still blowing cold the full details of the dryer are as follows MODEL 42AW. 0312 42A 15000/22.2500W HEATER.200 MOTOR.2700 MAX.230-240V.50HZ.13AMP.i would grateful for any advice on what is wrong and what part I need and were to get it and how much I have all ready had the back off the dryer and looked at the reset but but still not working thank you for your time and any help in this matter w p yemm