Look for scorch marks or other damage on the top, left of PCB. There is MAINS VOLTAGE at this point on the PCB, so watch it! Due to a 'design oversight', the pin carrying mains from one of the plugs onto the board often overheats and becomes (partly) detached from the copper track on the back of the board. Matters go from bad to worse as there is less and less copper cross-section to carry the (quite high) current, driving both fan and pump!
Eventually the PCB itself gets hot, scorches and sometimes actually catches fire.
Total crepe!!!