From the technical reference for the IBM 5170:
"If no fixed disk drive is connected to the power supply, the load resistor must be connected to P10. The load resistor is a 5 ohm, 50 watt resistor."
5 ohm resistor on a 12V line will draw 2.4 amps from that line. This greatly satifies the requirement (found in the 5170 technical reference) that the minimum loading of the +12V line of the 5170's power supply is 2.5 amps.
Below is pictured the load resistor (caged) that IBM supplied.