how to fix condenser dryer -Zanussi zdc46130w. flashing red light?

this condenser dryer runs for about 4 mins, flashes red then stops after a beep.. turn off and try again but after 4 mins it does it again.. It is heating up and running fine, it just cuts out. checked filters, condenser, small hose at back for blockage. and valve on bottle?? all that i can see. maybe a sensor of some kind broken?? please help.. Thankyou