How can I find out what is causing thermostats to blow?

My hotpoint tdc60p was not getting hot. We bypassed the thermostats and the heating element was heating so thought we just needed to replace the thermostats. We did this but after using the tumble dryer for 1 load they seem to have blown again. Before they blew this time. The drying light was on but the drum wasn't tumbling.
Any ideas what is causing this and if it is worth fixing.