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Home›Repair guides›Cummins/Onan›Testing Exciter Rotor

Cummins/Onan RGA-IN1 — Testing Exciter Rotor

Testing & diagnosis

For the Cummins/Onan RGA-IN1, from the Cummins/Onan service manual.

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Procedure

  1. Disconnect main rotor field leads at F1+ and F2-.
  2. Disconnect lead wires from diodes CR1 through CR6.
  3. Test between exciter lead pairs T1-T2, T2-T3 and T1-T3. Resistance at 77°F (25°C) should be 540 milliohms ± 10%.
  4. For grounds: apply test leads between any CR lead and rotor laminations. Reading should be 100,000 ohms or higher.
  5. If not, exciter rotor may require oven drying and retest. A shorted rotor must be replaced.

Tools required

  • Wheatstone bridge or digital ohmmeter Amazon
  • insulation resistance meter or Megger Amazon

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

Specs & values

  • 540 milliohms ± 10% at 77°F (25°C)
  • 100,000 ohms or higher

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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