What sort of fans are they? If they use brushed DC motors, you can work out the stall current by measuring their resistance and dividing it into the supply voltage. Measure the resistance several times, rotating the shaft a little between readings, and take the lowest resistance.
I think they are brushed DC - typical radiator fan motors.
The resistance differs between them - the measurement I took was 1.8ohms and 2.6ohms
So, taking your calculation, 12 (lowest supply voltage) / 1.8 ohms = 0.15A ?
12 / 2.6 = 0.21A
That seems stupidly low.
They have a 50A supply fuse on them.