I have to add some additional information. The heat sink of the charger gets his cooling air via bypass from the PEM cooling fan. This means, even when you drive, you will receive all dust in the charger heat sink, blocking the heat exchanger. Because its in the bypass, when blocked, all air will go to the AC-Inverter heat sink, no change to cool down the charger unit. I will be able now to flush back the charger heat sink by compressed air.