my hotpoint dryer ctd85 is showing f10 and f8?

Hi, my tumble dryer which is a hotpoint ctd85, is showing f10 and f8. It is blowing cold air out and wont turn off by button. I have cleaned out the full vent and draw, switched it back on and it still showed f10 then changed to f8 and would not turn off until i opened the door. Please can you help me, I cannot afford a new one, due to my combi boiler breaking down last week and I have had to replace that.
Any information would be great.

Linda Nelson
September 2009