I recently bought a 2012 Scion tC. The other day the red coolant light was blinking. I noticed the ac having a problem with cold air. I was stuck in traffic in 100+ weather.
I turned the A/C off and drove home with no more over heating light. I got Home popped the hood and checked. I saw only one radiator fan running. Turn the air back on, checked the fans again and only the one fan was still running.

This is is what I have done:
I’ve replaced the relay for the fans so I know they are good. I've ran direct power from the battery to the fan that wasn’t coming on. It turns on perfectly.
I've switched the plugs for the 2 fans and drove it to see what would happen. Only one fan came on still. It’s the other fan though because I switched the plugs for them

The only other thing I can think of is the coolant temperature sensor. I ordered one and it will be here Wednesday. I don’t see how that would only turn one fan on but I could be wrong.
If anyone has any other opinions please let me know. Also i tried looking for this in the threads but could not find anything. if this problem has been solved please give me the link.

Thank you.

Update

i did some more test on it today. I used a multi volt meter to determine if the relays are all good and they are.
i test to see if there is continuity from relays to connection ports, there is, and is also receiving 12 volts

Another update

i replaced the coolant temperature sensor and still hasn’t solved the problem. Only one fan is still coming on

I had the same problem on a similar car. I replaced the entire fan assembly which I got at my local parts store and it solved the problem!