Hi,
If you unplug the coolant temperature sensor and the fans come on you know the circuit is good. So, I have a feeling there is power lost to the relay. If you want, here is a link that explains how to test a relay.
https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit
You have already done a lot. I just noticed you didn't mention the relay or fuses.
I attached two pics below showing the entire wiring schematic for the fans. I highlighted the power supply. Realizing the fan turns on when you disconnect the sensor, I don't see a problem with the HD fuses. It's the 5 amp fuse (number 28) under the dash on the right side.
Check the fuses indicated. In addition to checking the fuses, make sure there is power to and from them. Here is a link you may find helpful:
https://www.2carpros.com/articles/how-to-check-a-car-fuse
Let me know.
Take care,
Joe
See pics below.
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Friday, May 28th, 2021 AT 8:52 PM