Need help! Gas engine overheating. Cannot resolve.

Thanks @rjparker ! I had to use engine body as ground as the battery is in the trunk. The positive connection from battery is accessible from engine compartment, but not negative. Tomorrow I will try to remove battery from a different car and test it with both positive and negative from that battery, this way I will not have to use engine body as ground. I hope it works that way, don't even want to think about replacing the fan. Just so that I am clear, in my earlier test I had disconnected fan connector from original wire coming from the car battery.

 

If you have properly applied 12v directly to the fan connector it almost can not work from the normal circuit. Meaning the passenger side motor is bad.

However the back probing method for feeding power does leave a little uncertainty about the connection you made since we are not measuring separately on the downstream wires.

In a similar manner back probing the normal circuit for voltage while connected leaves significant uncertainty if you supply a separate ground.

The normal connected circuit for that motor is always grounded.