Cummins/Onan RDJF Generator Set

⚠ Avoid overcharging.

1. Set slide tap on adjustable resistor R21 in generator air outlet to give about 2 amperes charging rate.
2. If charge winding AC output is below 19 volts on 12 volt battery charge models, 38 volts on 24 volt models, 50 volts on 32 volt models, test charging circuit for opens or grounds.
3. If a separate automatic demand control is used, adjust charge rate for maximum 4.5 amperes.

Tools: AC voltmeter

1. If set has a voltage adjust potentiometer (R22) on the meter panel, set pointer halfway between minimum and maximum positions.
2. With unit running at no load, turn generator voltage potentiometer R26 on VR21 clockwise to increase output voltage; turn R26 counterclockwise to decrease output voltage.

1. With generator set running at no load, turn potentiometer R27 to a position where voltage tends to be unstable or hunt.
2. Turn R27 clockwise slowly until voltage first stabilizes.

Tools: hydrometer

1. Check charge condition of battery with a hydrometer.
2. Specific gravity should be between 1.290 and 1.225 when 75 percent charged. If not, recharge the battery.
3. Check electrolyte level. Add approved water to keep electrolyte at its proper level.
4. If battery will not recharge, replace it. Keep battery connections tight and clean.

Tools: feeler gauge

1. The start-disconnect switch is located on the gear cover on the side of the engine above the oil filter.
2. The switch opens when engine stops and closes when engine speed reaches about 900 rpm.
3. Check switch contacts for pitting. If necessary, loosen stationary contact and adjust point gap at 0.040 inches.
4. Replace burned or faulty points.

⚠ Note carefully the direction of mounting of any rectifier removed. It must be remounted in its original direction.

Tools: ohmmeter

1. Disconnect one lead from, or remove, each rectifier for its individual test.
2. Connect ohmmeter across rectifier contacts and observe meter reading.
3. Reverse connections and compare new reading with first reading.
4. If one reading is considerably higher, rectifier is satisfactory. If both readings are low or open, replace with new identical part.

Tools: voltmeter

1. Connect 12 volts on one side of relay coil and ground other side. If coil activates, relay is operating.
2. Connect a 12 volt source to one side of relay contacts.
3. Connect a voltmeter to other side of relay contact and to ground. If 12 volts appears when relay is energized, relay is good.
4. If relay has more than one set of contacts, each set must be checked.

Tools: ohmmeter

1. Remove battery B+ cable.
2. Disconnect one side of resistor and using an ohmmeter measure across resistor for an accurate reading.

Tools: voltmeter

1. Apply 12 volts to terminal marked BATTERY.
2. Jumper a ground wire to terminal marked S.
3. Solenoid should activate.
4. If solenoid is good, 12 volts can be read between terminal S and ground.

Tools: voltmeter

1. With the starting motor operating, check voltage drops from battery ground terminal post to cylinder block, cylinder block to starting motor frame, and battery positive post to battery terminal stud o
2. Normally each should be less than two volts.
3. Thoroughly clean all connections in any part of the circuit showing excessively high voltage drops.

Tools: ohmmeter

1. Remove battery B+ cable.
2. Place ohmmeter leads across switch.
3. Activate switch. If meter reads continuity, switch is good.

Tools: Wheatstone Bridge, ohmmeter

1. Use a Wheatstone Bridge. Disconnect main rotor field leads at F1+ and F2-.
2. Disconnect lead wires from diodes CR1, CR2, CR3, CR4, CR5 and CR6.
3. Test between exciter lead pairs T1-T2, T2-T3 and T1-T3. Resistance should be 0.5 to 0.6 ohms at 20 C (68 F.).
4. Connect leads of ohmmeter between each CR lead and exciter rotor laminations; use RX 100 scale; reading less than infinity indicates defective ground insulation.