Amp draw at different voltage
If the radiator fan  requires 24 amps at 12 volts DC, that is 12 V X 24 A = 288 Watts. If you are going to convert 110 volts AC or DC to 12 volts DC with 80% efficiency, that is 288 / .8 = 360 watts. At 110 volts DC, that would be 360 / 110 = 3.3 amps. If you are using a transformer with a rectifier and filter to convert from 110 or 120 VAC, the rectifier and filter will cause some harmonic current that will increase the current without increasing the power but reducing the power factor. The current might be 5 amps or so.