vanessa, there are a number of reasons that may cause your dryer to not heat, there are thermostats on the rear of the dryer just above the heater element which may need replacing, there is the heating element itself which may need replacing, there is an other thermostat above the door which may need replacing or there could be a fault on the timer unit. The most common fault is the thermostats on the rear of the dryer. I would suggest however that you use a qualified service engineer to check your machine and carry out the work as he will have specialist testing equiptment to identify the fault and also be able to carry out the repair in a safe manner. Tumble dryers can be very dangerous.
I hope this helps.
neil, January 2008