Rotor Check

Check the continuity between the slip rings of the field coil. If the resistance value is not within the standard value, replace the rotor.
Standard value: approximately 2 - 5 Ω

Fig 1: Checking Slip Rings Continuity
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Check the continuity between the slip ring and the core. If there is continuity, replace the rotor.

Fig 2: Checking Continuity Between Slip Ring & Core
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.