Thanks for the great explanation Arthur. BTW, the blown OVP relay was a new one installed 2 years ago 000-540-67-45. My backup OVP relay is also a new one with the same part number. Just strange that it blew coincedently during this event.

I will read more about HFM/SFI system operation. I do own an old CD set (WIS_09_2004) but it always comes up in German and I have never taken the time to corret that. I will take the time now!

BTW, I found another relay for the Aux Fans thats exactly like the green Fuel Pump relay.. These relays can be swapped for testing possible relay failure.

Again thanks for your help..
Ending this thread..