Cummins/Onan MDKD Generator Set

⚠ Settings apply only to the control panel where the change was made, not to remote panels.

1. Press SCREEN on any GEN STATUS screen.
2. Press NEXT to toggle between Brightness and Contrast.
3. Press the right or left arrow to increase or decrease.
4. Press BACK to save the settings and return to GEN STATUS.

⚠ Accidental or remote starting can cause severe personal injury or death.

Tools: Insulated wrench

1. Disconnect the negative battery cable.
2. Remove the belt guard or enclosure top panel and access doors.
3. Loosen the alternator pivot bolt, then the adjusting bracket bolt.
4. Pivot the alternator out to tighten the belt.
5. Check tension by applying 10 kg (20 pounds) to the middle of the pulley span.
6. Tighten the alternator bolts, secure the guard, and reconnect the battery.

⚠ This procedure does not change AC output voltage. Have a trained and experienced person adjust AC output voltage, if necessary, before calibrating the digital display voltmeter.

Tools: Accurate AC voltmeter

1. Press SETUP, then NEXT to highlight AC Voltmeter Calibration.
2. Press the up or down arrow until the displayed voltage matches an accurate AC voltmeter.
3. Press BACK to save the selection and return to GEN STATUS.

1. Press SETUP on any GEN STATUS screen.
2. Press NEXT on the DISPLAY SETUP screen to highlight UNITS.
3. Use the up or down arrow to select SAE or METRIC.
4. Press BACK to save the selection and return to GEN STATUS.

Tools: Voltmeter

1. With starter motor operating, check voltage drop from battery negative post to cylinder block.
2. Check voltage drop from battery positive post to battery terminal stud on solenoid.
3. Each should normally be less than 0.3 volts.
4. Clean all connections in any part of the circuit showing excessive voltage drop.

⚠ Battery electrolyte can cause severe eye damage and burns; wear goggles, rubber gloves and a protective apron.

Tools: Hydrometer

1. Check charge condition of the battery with a hydrometer.
2. Electrolyte specific gravity should be about 1.260 fully charged at 80°F (27°C).
3. Add distilled water to keep electrolyte at proper level and recharge.
4. If battery will not recharge, replace it.

Tools: Voltmeter

1. Apply battery positive (B+) to the terminal marked S.
2. Connect a ground wire to the solenoid mounting bracket.
3. Solenoid should activate.
4. Battery voltage should be read between terminal 1 and ground if contacts good.
5. Voltage drop across contacts should never exceed one volt.

Tools: Wheatstone bridge or digital ohmmeter, Megger or insulation resistance meter (500 VDC or more)

1. Disconnect F1+ and F2- exciter field leads from terminal block in generator end bell.
2. Measure resistance between field leads with a Wheatstone bridge or digital ohmmeter.
3. Resistance should be 11.16 to 13.64 ohms at 77°F (25°C).
4. Apply 500 VDC or more between either field lead and the exciter stator lamination.
5. Insulation reading should be 1,000,000 ohms or greater.
6. A shorted stator must be replaced.

Tools: Megger or insulation resistance meter (500 VDC or more), Digital ohmmeter

1. Remove rotor leads F1+ and F2- from the rotating rectifier assemblies.
2. Connect test leads between F1+ and rotor shaft, then between F2- and rotor shaft.
3. Meter should register 1,000,000 ohms or greater.
4. Use a digital ohmmeter to check resistance between F1 and F2 leads.
5. Replace a grounded rotor with a new identical part.

⚠ Some generators have ground connections to the frame; check wiring diagram.

Tools: Megger or insulation resistance meter, Wheatstone bridge

1. Isolate all stator leads for testing.
2. Apply 500 VDC or more and test each stator winding for short to laminations.
3. Reading less than 1,000,000 ohms indicates a questionable stator; oven dry and retest.
4. Test continuity between coil leads; all pairs should have equal resistance.
5. If a winding is shorted, open or grounded, replace the stator assembly.

Tools: Ohmmeter

1. Disconnect all leads from the rectifier assembly to be tested.
2. Connect one ohmmeter lead to F1+ stud and to CR1, CR2, CR3 in turn; record values.
3. Connect one lead to F2- stud and to CR4, CR5, CR6 in turn; record values.
4. Reverse ohmmeter leads from steps above and record resistance of each rectifier.
5. Readings must be high in one test and low in the other; otherwise replace assembly.
6. Replace defective rectifier assembly with a new identical part.

⚠ Fuel vapor fire/explosion hazard

⚠ Heavy set can cause injury if dropped

1. Disconnect generator set negative (-) battery cable at the battery terminal.
2. Disconnect generator set positive (+) battery cable from the wire harness.
3. Disconnect the remote control plug wire from the generator set, if applicable.
4. Disconnect generator load wires and tag for identification when reconnecting.
5. Disconnect exhaust system and support brackets or hangers to allow set removal.
6. Disconnect fuel line at the generator set housing and plug the fuel line end.
7. Verify the generator set is adequately supported before loosening mounting bolts.