While you wait for answers, we may have found some information which could help you.
Click here for Thermostat Dryer HeatBosch Classixx not heating even after trying red button reset ?
Bosch excel condenser dryer 6307?
Tumble dryer not drying clothes?
Bosch exxcel condenser dryer WTL6307GB?
belt to slack. ?
Bosch Exxcel 7 WTW863S1GB damp clothes, clogging filter?