the machine is over heating, the heat is staying or building up around the heater (the air is not being circulated correctly in the machine) the condenser at the bottom of the tumble dryer is probably blocked and needs cleaning. ( take outside & run water from a garden hose through it ) this is the best way of it cleaning out.
if you need any help parts try this site.
www.candmdomesticappliances.co.uk
paul, June 2008