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Home›Repair guides›Cummins/Onan›Testing Exciter Rotor (Test J)

Cummins/Onan — Testing Exciter Rotor (Test J)

Testing & diagnosis

From a Cummins/Onan service manual covering: DL4, DL6, DL6T. Check it applies to your exact model before use.

Applies to: Cummins/Onan DL4, Cummins/Onan DL6, Cummins/Onan DL6T

Procedure

  1. Use a Wheatstone Bridge for this test.
  2. Disconnect main rotor field leads at F1+ and F2- and disconnect leads from diodes CR1-CR6.
  3. Test between exciter lead pairs T1-T2, T2-T3, and T1-T3; resistance should be 0.6 to 0.7 ohms at 68 deg F (20 deg C).
  4. Connect ohmmeter between each CR lead and rotor laminations; less than one megohm indicates defective ground insulation.

Tools required

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

Specs & values

  • 0.6 to 0.7 ohms at 68 deg F (20 deg C)

Full service-parts list: Cummins/Onan DL6 →

Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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