Cummins/Onan C20 N6 Generator Set

⚠ Do not rotate the center section of the valve beyond the detent.

Tools: 6 mm external hex wrench

1. From the Main screen, select Menu; hold the Next key at least 5 seconds to view the Config Menu.
2. Highlight 'Config' and click Enter. Use the Next key to navigate to the Fuel Type field; select NG or LP.
3. Do not change the number in the Config field.
4. Use a 6 mm external hex wrench to rotate the center section of the fuel valve.
5. Turn the center section clockwise until the detent is reached; do not rotate beyond this point.
6. Keep selecting the Back button to save the settings and return to the Main screen.

⚠ Failure to configure will result in Fault Code 37.

1. From the Main screen, select Menu.
2. Press and hold the Next key on the Menu screen for at least 5 seconds to view the Config Menu.
3. Highlight 'Config' and click the Enter key. The Generator Config screen appears.
4. Use the Next key to navigate to the Config field. Use the arrow keys to select the appropriate config option (20 = C20N6H/C20N6HC, 21 = C17N6H, 22 = C13N6H).
5. Use the Next key to navigate to the Fuel Type field. Select NG (natural gas; default) or LP (liquid propane).
6. Keep selecting the Back button to save the settings and return to the Main screen.

1. From any Information Menu, hold down the up and down arrows simultaneously for two seconds to access the Service Menu.
2. Select Fault History.
3. Active faults are displayed first, followed by Fault History screens newest to oldest.

Tools: Multi-meter, Soapy water solution

1. Disconnect the four harness leads from the fuel solenoid coils.
2. Check that battery voltage is being supplied through the generator set harness using a multi-meter between FSOL1+/FSGND1 and FSOL2+/FSGND2 while trying to start.
3. Verify that the voltage is 10.2 VDC. If no voltage, check for bad wiring; if less than 10.2 VDC, check for bad wiring or discharged battery.
4. Check for proper solenoid operation by applying 12 VDC to a coil and listening/feeling for activation. Repeat for all solenoids.
5. If either solenoid does not activate, replace the gas valve assembly.
6. Check for fuel leaks at the solenoid with a soapy water solution on pipe threads and around the base; tighten or replace as required.

⚠ Automated Machinery: accidental or remote starting can cause severe personal injury or death.

Tools: Ohmmeter

1. Shut down and disable the generator set; disconnect the negative (–) battery cable and reconnect it last when done.
2. Disconnect the leads going into and out of the circuit breaker (two leads from the alternator at the top L1 and L2, and two from customer wiring at the bottom L1 and L2).
3. Check continuity: with the breaker on, very low resistance between the L1 lugs and between the L2 lugs.
4. With the breaker off, the continuity check between L1 and L2 pairs should show open.
5. Replace the breaker if either of the continuity tests fails.

⚠ Disconnect the AVR before doing any insulation resistance test. Discharge the windings by shorting to earth through an earthing rod for at least 5 minutes.

Tools: Ohmmeter, Megger or insulation resistance meter, Wheatstone bridge (0.001 Ohms precision)

1. Test the rotor for grounded, open and shorted windings using an ohmmeter, testing at the brush block terminals first.
2. For rotor ground resistance, set the ohmmeter to the highest scale or use a megger; touch one probe to the rotor shaft and the other to a slip ring.
3. For rotor winding resistance, connect each meter test lead to a separate slip ring and compare to the resistance table.
4. Test for a short between the main windings and the quad windings.
5. For stator ground resistance, touch one test probe to the stack and, in turn, the other to each stator lead.
6. Measure stator winding resistance with a meter having precision down to 0.001 Ohms.
7. Measure each winding to the stator laminations to check for bad insulation.

⚠ Ensure that the generator set engine has cooled down before adding or draining the oil.

1. Ensure that the oil fill cap area is clean, and prevent debris from entering the engine.
2. Add the appropriate amount of oil, based on the engine oil level check.
3. Recheck the engine oil level. Based on the results, add or drain oil.
4. Clean up and dispose of any oil in accordance with local/state regulations.

1. Wipe dirt from the cover and upper portion of the air cleaner.
2. Lift tab and turn end cover counter clockwise.
3. Pull the end cover away from the housing.
4. Remove the media from the housing.
5. To install: insert the media into the housing, install the end cover onto the housing, turn clockwise until the latch snaps into place.

⚠ Holes, loose-end seals, dented sealing surfaces, corrosion of pipes render the air cleaner inoperative and require immediate element replacement.

1. Loosen the strap clamp.
2. Wipe away debris around the air cleaner connection to the engine.
3. Remove the dirty cleaner and dispose of the dirty element per local requirements.
4. To install: install the air cleaner and tighten the strap clamp.

⚠ Make sure the brushes are aligned correctly with the slip rings; otherwise they may break when the generator set is started.

Tools: Scotch Brite pad or commutator stone

1. Disconnect the field leads from the brush block (F1, F2).
2. Remove the two mounting screws.
3. Withdraw the brush block from the alternator end bell.
4. Inspect the brush block: if either brush is shorter than 11 mm (7/16 inch), binds, or is damaged, replace the brush block assembly.
5. When installing the brush block, keep the brushes retracted with the wire through the hole; remove the wire after bolting the block in place.
6. If the slip rings have grooves, pits, or other damage, use a Scotch Brite pad or commutator stone to remove light wear or corrosion.

⚠ Contact with used engine oil can cause cancer or reproductive toxicity.

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

1. Open the generator set's circuit breaker to prevent the ATS from transferring to generator set source when manually starting.
2. Manually start the generator set and allow it to run 2 to 5 minutes to warm the engine oil.
3. Remove the access panels to get to the drain hose.
4. Stop the generator set and allow it to thoroughly cool. Disconnect the battery charger and the negative (–) battery cable.
5. Open the oil drain cap to release oil from the engine into the appropriate container, close it, and wipe it clean.
6. Place an appropriate container below the oil filter. Remove the oil filter by turning it counterclockwise and remove the old gasket.
7. Clean the filter mounting surface on the engine block.
8. Make sure the gasket is in place on the new filter and apply a thin film of clean oil to the gasket.
9. Install the new filter until the gasket just touches the block. Turn it an additional 1/2 to 3/4 turn. Do not over-tighten.
10. Add the appropriate amount of oil and check the engine oil level.
11. Reconnect the battery cables, positive (+) cable first, and reconnect the battery charger.
12. Operate the generator set with no load for approximately 5 minutes to check for leaks at the oil filter or oil drain hose.
13. Shut down the generator set, wait 5 minutes, and confirm the correct oil level. Check for leaks and repair any identified.
14. Dispose of the used oil and oil filter according to local environmental regulations.
15. Re-install the access panels and restore the original generator set settings, then close the generator set breaker.

⚠ Crankcase pressure can blow out hot oil and cause severe burns. Do NOT check oil while the engine is operating.

1. Pull out the dipstick and wipe it clean.
2. Clean off the area surrounding the dipstick port to prevent entry of debris into the oil pan.
3. Make sure that the engine has not been running for approximately five minutes.
4. Reinsert and fully seat the dipstick.
5. Remove the dipstick and check the oil level.
6. Reinsert and fully seat the dipstick.