blowing cold no rest button on back ?

Flippantly - diagnose and repair the fault.

I would guess that a fan blows air across a heating element and the warmed air is directed to the clothes tumbling in the drum.

The heater/fan combination has probably failed in some way - I would guess the heating element.

Again - somewhat flippantly - your choices are...
Do nothing
Buy a new dryer
Attempt diagnosis and repair yourself
Have somebody else diagnose and repair

Good luck...

Peccavi
September 2010