so like the title says I've been having this issue ever since having to put back the 5sfe motor into my car. Both radiator and A/C fan start to run the moment i turn the key to the "on" position. i tried unpluging both coolant temp sensors but they continue to run, my relays for the fans are working correctly so at this point im confused and exhuasted, the only thing i can think of is the ecu took a dump on me and is telling the fans to stay on all the time BUT i dont have another ecu to swap it with and i dont want to spend the money to do so and i end up being wrong. so has anyone else ran into this problem or have any suggestions for me. i really wanna fix this cause im sure its the reason my car runs like **** in cold start and takes forever to warm up properly.

this happens if the plug at the bottom of the radiator is unplugged. double check its connection

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are you talking about the plug that go to the ECT on the radiator?

Smaay, isn't it so that if it's disconnected, the fans wont turn on at all? I believe in order to run the fans constantly you had to bridge the connector. In that case I would say the sensor is stuck in closed-loop

If the fan's power is disconnected, then yes it won't run. If the water temperature fan switch is disconnected, or faulty, the fan will run all the time -- it's Toyota redundency.

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^^ correct, its not seeing the sensor so it turns the fans on.

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so should i try to change out the switch thats on the bottom corner of the radiator?

its not a switch, its a sensor. and yes thats a good start

Toyota refers to it as a switch, specifically water temperature switch because it opens and closes the circuit itself based upon temperature (93C) rather than signalling something else. It's not a switch that we operate, certainly.

You can easily test the water temperature switch with a pot of water. Below 93C, there should be no continuity between the terminals of the switch. This keeps the fan power circuit open and the fans off. Above 93C, the switch should close, establishing continuity between the terminals and running the fan.

Galcobar is right.
I had the same problem. Water temperature switch was broken. Replaced it and now it's working fine.