Okay, I disassembled the printhead to find the correct wires for the fans. It turns out the center and left fan wires had been switched. I was able to remedy this by switching the 2p connectors in the wiring loom. However the cable lengths are not quite correct (center fan cable is 3 cm too short, left one too long) which leaves me to believe they are cut to size on assembly of the printhead. After that a 2p connector is crimped on. If you mistakingly switch the cables on cutting you get exactly what I had. But all seems ok.
I do find it a little bit odd this made it through quality control. The problem is quite apparent when you switch the printer on.
The hot end seems to work fine still. Everything is working as intended, but now I have to go and find out the best ABS temperature/cooling settings all over again .. For now 50% fan seems to work best.. Before it was 15% fan ;-),
Thanx for the help!
Vincent