The correct way to trouble shoot with parts swapping is by taking the suspected bad part to a known good machine, and seeing if the problem follows the part or not. Doing it the other way leads to a lot of mistakes.

I had a similar problem with a crown rr5200 recently. There were diodes in the cooling fan motor wire harness that had shorted, I don't know what caused the short. The solution was a new fan subharness. Cutting out the diodes was a temp fix to see if the fans would work. Unfortunately the diodes could be internal in the fan motors. Also you should check the condition of all the connector pins from the CPU to the fan motor. Take a voltage reading on the fan circuit wires before and after each connector.