Procedure to Restore the Residual Magnetic Field on Brushless Alternators

3116 (S/N: 4PG3542-UP; 2MR277-UP)
3126B (S/N: BEJ154-UP; DCS739-UP)
3176C (S/N: 2AW375-UP)
3196 (S/N: 1DW483-UP)
3304 (S/N: 04B27163-UP; 23C2672-UP; 66D50755-UP; 67U10731-UP; 38S17134-UP; 4XB1081-UP; 10E2942-UP)
3306 (S/N: 64Z2682-UP; 85Z8567-UP)
3306B (S/N: 7JB8011-UP; 5GZ314-UP)
3408E (S/N: 7PR414-UP)
3412E (S/N: 4CR500-UP)
3508B (S/N: ZAD245-UP)
3512 (S/N: ZAF114-UP)
3512B (S/N: BLF176-UP)
3516 (S/N: 8TW1-UP)
3516B (S/N: FDN1322-UP; 7RN1953-UP; ZAP186-UP; 2JW414-UP; 8NW1-UP)
C-10 (S/N: BCX130-UP)
C-12 (S/N: BDL156-UP)
C-9 (S/N: CLJ306-UP)
C7 (S/N: JRA288-UP; JTF387-UP)
C9 (S/N: X3R1-UP)
G3408C (S/N: BAZ2218-UP)
G3520B (S/N: BGW1-UP)
Generator Set:
3406 GEN SET (S/N: 4ZR351-UP)
3406C GEN SET (S/N: KPS2010-UP; 9ES1-UP; LRX1-UP)
3456 GEN SET (S/N: BGA1-UP; CCB481-UP; CAH1-UP; CBX620-UP)
C15 GEN SET (S/N: PEC101-UP; X4R1-UP)
C18 GEN SET (S/N: STD149-UP; PEJ101-UP; STM1-UP)
C27 GEN SET (S/N: DWB233-UP)
Industrial Engine:
3406B IND (S/N: 6TB5569-UP)
3406C IND (S/N: 3ER525-UP)
3406E IND (S/N: 6BR616-UP)
3412E IND (S/N: BDT4483-UP)
C-15 IND (S/N: BEM135-UP)
C-16 IND (S/N: BFM148-UP)
C15 IND (S/N: JRE102-UP)
Marine Engine:
3408C MARINE (S/N: 9ER311-UP)
Power Module:
PM3508 (S/N: BLM244-UP)



This Special Instruction describes the procedure that is used in order to restore the residual magnetic field in the alternator.



Charging problems may be encountered when you install brushless alternators that are new or remanufactured. The alternators may not begin to charge in some instances. The alternators may be considered faulty. Brushless alternators are self-excited. Self-excited alternators begin to charge at start-up, without the use of an external power source. Self-excited brushless alternators use residual magnetism in order to generate sufficient current to start the charging process. Charging problems with these alternators usually result when the residual magnetic field in the alternator is reduced below the level that is needed to excite the alternator. The following factors can lead to residual magnetism that is reduced:


  • Rough handling
  • Storage temperatures above approximately 38° C (100° F)
  • Extended storage periods of more than three to six months
  • Manufacturing tolerances in the alternator
  • Disassembled for repair



Before returning or replacing a brushless alternator for failing to charge, use an external power source to restore the residual magnetic field. Use a jumper wire in order to connect the positive “+” output terminal of the alternator to the “R-Terminal” of the alternator for approximately two seconds. Refer to Illustration 1. This temporary connection should provide sufficient current from the vehicle batteries in order to restore the residual magnetic field in the alternator. If the alternator failed to charge due to one of the causes above, this procedure should restore residual magnetism. If the residual magnetism is restored, self-excitation will occur at the next start-up.

Note: The unit must not be rotating while the field is being flashed. If you rotate the alternator during this procedure, you may damage the unit. The unit should be electrically connected. The unit must have battery voltage at “B+” and the unit must be properly grounded. Touch a jumper wire from “B+” to the “R-Terminal” for no more than two seconds. Be careful not to touch ground (case) with the ends of the wire. During the two second period, there should be a small flow of current of about two to five amperes, depending on the model number and system voltage. The current flow is between two to three amperes on 24 volt units. You should notice a tiny spark when the wire is touched to the “R-Terminal”. If a large arc occurs when you flash the field, the “R-Terminal” of the alternator has a short to ground and the unit should not be used.

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