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My car overheated in stop and go traffic yesterday. The gauge never read over about 40%, the heat coming out of the vents was extremely hot, the radiator was full, but the reservoir looked empty or very low. The fans were not kicking on at all. I tried turning on the AC to get that fan on, but it only stayed on briefly. I replaced the fan relay a while ago, but its been cold out so it may not have ever needed to turn on. I swapped out the horn and fan relay to test, and the fan still never turned on.

I don't know anything about cars, but my guess is that the temperature sensor is reporting back incorrect to the gauge in the car which is causing the fan to not turn on. Additionally, the thermostat is either frozen closed, or the reservoir was just empty. Does that sound about right? Thank you for any help or insight you might give me.