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Home›Repair guides›Test Rotor Continuity

Cummins/Onan — Test Rotor Continuity

For these Cummins/Onan models: 04SXINIA, 102SXIN1A, 208, 2SX5IN, 2SXIN, J-Series, O6SXIN1A, O7SXIN1A.

Applies to: Cummins Onan 04Sxinia, Cummins Onan 102Sxin1A, Cummins Onan 2Sx5In, Cummins Onan 2Sxin, Cummins Onan J Series, Cummins Onan O6Sxin1A, Cummins Onan O7Sxin1A

Procedure

  1. Remove the brushes so none touch the collector rings.
  2. Using an ohmmeter, test for grounding between each slip ring and the rotor shaft.
  3. Test for a short or open circuit in rotor winding by measuring resistance of winding.
  4. It should measure between 3.5 and 4.8 ohms for the JB and between 2 and 3 ohms for the JC (at 70°F).
  5. If an accurate ohmmeter is not available, check the rotor for open circuit or grounding with an AC test lamp.
  6. Replace the rotor if it is grounded, or has an open circuit or short.

Tools required

  • Ohmmeter
  • AC test lamp

Specs & torque values

  • Rotor winding resistance JB: 3.5-4.8 ohms
  • Rotor winding resistance JC: 2-3 ohms (at 70°F)

Source: manual:Onan Magneciter Service- SECTION 4. REVOLVING FIELD GENERATORS.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.