Bosch Exxcel dryer- Stops with ‘Empty Filter’ warning

Hi all,

I have a Bosch WTL6305GB/ 01 (6kg Exxcel condenser model). Roughly 10/15 minutes into a cycle, the dryer stops with a warning beep, and the ‘Empty filter’ light comes on. The heater is working and cycle seems to reach normal temperature.

I have checked the basics so far:

-Lint screen has been washed (checked the mesh is breathable, no problems here)
-Condenser unit was a bit clogged- I’ve soaked and rinsed this, looks quite clear now
-No other obvious fluff causing obstructions in the airways, checked the heater area is clear, and wiped some fluff build up from a temperature sensor here.

The fault occurs on any of the programs I have tried (low and high heat)- could anyone advise how the ‘Empty filter’ warning is triggered, is it temperature related from one of the sensors?

Any advice appreciated.

Thanks

Rob