2007 530i-cooling fan not coming on.

Hey guys,
I need a little help. I have a 2007 530i with about 58,000 miles on it. A few weeks back I was in Albuquerque and it was dang near 100 degrees. The car said "Engine too hot" and told me to take it easy. Looks like that is a first stage overheating warning. I determined that the aux fan was not coming on when the AC was on. So I pulled what I am 90% sure in the power feed to the fan, the big molded plug to the left of the fan. I had 12-13 volts DC at that plug. I cleaned it up, checked the connections and put it back together. The fan came on and I had no problems for two weeks. I praised myself as a master mechanic and went on.
Today it did the same thing again. I pulled the plug and again I have 12 VDC at the plug. But the fan will not come on. Today I got a second stage "Car too hot, pull over, do not open the hood. etc".
Is that indeed the power feed to the aux. fan? I see some threads about a fan clutch but I am pretty sure my fan is electric only. It seems to have no connection to the engine pulleys. Is it as cut and dry as 12VDC to the fan and it should run, or do the wires go to some other control when they go down after that plug? I see people talke about a resistor sticking open as well. But it is not just losing low speed, it does not work at all. I am pretty sure the fan is ok.

Any thoughts would be much appreciated.

Thanks

For the same issue, my car sits at the dealership as I type. I will update you about mine tomorrow.

I figured out that the 12VDC is always there. The third wire is a signal wire telling the fan what speed to come on. Does anyone know the range of the signal that it receives?