bosch tumble drier is not getting hot just blowing cold air?

It is most likely that the 'overheat thermostat' has tripped.
This can be caused by failure to clean the small compartment located on either the left or right hand rear side (depending on where the exhuast pipe is fitted ,which collects debris and when blocked reduces the air flow.
Pull the unit out ,unscrew the round disc which will expose the compartment and clean.
This may correct the problem but otherwise you may have to reset the thermostat.
Sorry,that I can't advise you on.

George King
May 2007