Cummins/Onan TGHAA Generator Set

⚠ AC power within the cabinet and the rear side of the cabinet door presents a shock hazard.

Tools: small screwdriver

1. Open the cabinet door.
2. Use a small screwdriver to turn the HI Alm or LO Alm adjustment potentiometers counterclockwise to decrease or clockwise to increase the alarm voltage.
3. When finished, close and lock the cabinet door.

⚠ Ignition of explosive battery gases can cause severe personal injury. Do not smoke or cause any spark, arc, or flame while servicing batteries.

Tools: hydrometer, small screwdriver, accurate voltmeter (0.5% accuracy)

1. Turn the generator set operation selector to Stop and disconnect the starting battery (negative [–] lead first).
2. Connect the fully charged battery (negative [–] lead last) and verify charge condition with a hydrometer.
3. Connect the voltmeter directly to the battery terminals and measure the voltage.
4. Compare the voltage reading with the recommended float voltage in Table 3-1.
5. Turn the adjustment potentiometer counterclockwise to decrease or clockwise to increase the float voltage; wait five minutes for stabilization.
6. Close and lock the cabinet door, disconnect the voltmeter, and disconnect the test battery (negative [–] lead first).
7. Reconnect the generator set starting battery (negative [–] lead last) and place the operation selector switch in Auto or Remote.

⚠ AC voltages and currents present an electrical shock hazard that can cause severe personal injury or death. Make sure that both AC power sources are disconnected.

⚠ Incorrect placement of transformer jumper wires can cause damage to the control when power is applied.

1. Disconnect both AC power sources (Normal and Emergency).
2. Place the 3-Phase/1-Phase switch (S1) on the control circuit board in the appropriate position.
3. Place the transformer jumper wires on the control board in the appropriate positions (refer to sheet 3 of the schematic and wiring diagram package).

⚠ Wrong fuel selection can result in hard starting, poor genset performance and fault shutdown.

1. For LPG: turn the fuel type selector on the carburetor clockwise as far as it will go.
2. Remove the cap over the hose fitting on the air cleaner adapter and clamp the balance hose onto the fitting.
3. For Natural Gas: turn the fuel type selector on the carburetor counterclockwise as far as it will go.
4. Disconnect the balance hose from the hose fitting and clamp a hose fitting cap over the hose fitting.
5. Secure the balance hose out of the way of vibrating parts so it will not get pinched.

⚠ Wrong fuel selection can result in hard starting, poor genset performance and fault shutdown.

Tools: clamps

1. For LPG: turn fuel type selector on carburetor clockwise as far as it will go, remove cap over hose fitting on air cleaner adapter, clamp balance hose onto fitting.
2. For Natural Gas: turn fuel type selector counterclockwise as far as it will go, disconnect balance hose from hose fitting on air cleaner adapter, clamp hose fitting cap over hose fitting.
3. Secure balance hose out of way of vibrating parts.

⚠ High gas supply pressure can cause gas leaks which can lead to fire and severe personal injury or death.

Tools: Manometer (at least 14 inch / 350 mm WC)

1. Close the gas supply shutoff valve.
2. Remove the 1/8 inch pipe plug from the regulator test port and connect a manometer (scale range at least 14 inches / 350 mm WC).
3. Open the gas shutoff valve and try starting the genset.
4. While the genset runs at no load, adjust the gas supply pressure regulator to obtain 11 inches (279 mm) WC.
5. If the genset will not start, jumper the fuel solenoid open and then check and adjust pressure.
6. Check gas supply pressure under full load; if it drops below minimum the supply piping may be too small.
7. Disconnect any jumpers and thread in and tighten the pressure test port plug.

⚠ AC power within the cabinet and the rear side of the cabinet door presents a shock hazard.

Tools: screwdriver

1. Move the calibration switch (S4) to the CAL position (100% pickup setting).
2. Turn on Normal source and check for nominal voltage.
3. Slowly turn the Normal calibration (Cal) potentiometer clockwise until the Normal Available lamp just turns ON.
4. Turn on Emergency source and check for nominal voltage.
5. Slowly turn the Emergency calibration (Cal) potentiometer clockwise until the Emergency Available lamp just turns ON.
6. Move the calibration switch to the 85% position (sets 85% pickup and 75% dropout).

⚠ AC power within the cabinet and the rear side of the cabinet door presents a shock hazard.

Tools: screwdriver

1. Normal source: turn Normal Pickup pot fully clockwise to 100% pickup.
2. Turn Normal calibration (Cal) pot fully counterclockwise.
3. Turn Normal Dropout pot fully clockwise to 97% dropout.
4. Turn on Normal source and check for nominal voltage.
5. Slowly turn the Normal Cal potentiometer clockwise until the Normal Available lamp just turns ON.
6. Emergency source: turn Emergency Pickup pot fully clockwise to 100% pickup.
7. Turn Emergency Cal pot fully counterclockwise.
8. Turn Emergency Dropout pot fully clockwise to 97% dropout.
9. Turn on Emergency source and check for nominal voltage.
10. Slowly turn the Emergency Cal potentiometer clockwise until the Emergency Available lamp just turns ON.
11. Turn off both power sources. Proceed to Undervoltage Pickup and Dropout Adjustments.

Tools: 3/8 inch allen wrench, Feeler gauge

1. Adjust the valve clearance only when the engine is at ambient temperature.
2. Remove all parts that block access to the valve tappets.
3. Remove the spark plugs to make turning the engine easier.
4. Use a 3/8 inch allen wrench in the rotor through bolt to rotate the crankshaft counterclockwise until the right intake valve opens and closes.
5. Continue turning until the TC mark on the flywheel lines up with the TC mark on the gear cover (right piston at top of compression stroke).
6. Verify the right intake and exhaust valves are closed and there is no pressure on the valve lifters.
7. Measure clearance; the feeler gauge should just pass between the valve stem and valve tappet.
8. Turn the self-locking adjusting screw as needed to correct the clearance.
9. Turn the engine one complete revolution to align the TC marks and repeat for the left cylinder.
10. Replace all parts removed.

Tools: Cylinder compression tester

1. Start the genset and let it warm up.
2. Stop the genset and remove and inspect the spark plugs.
3. Insert the compression gauge nozzle into one of the spark plug holes, hold the throttle open and crank the engine.
4. Note the pressure indicated by the gauge.
5. Repeat the test on the other cylinder.
6. If pressures do not meet Specifications, refer to Engine Block Assembly.

⚠ AC power within the cabinet presents an electrical shock hazard. Disconnect all sources of AC power from the transfer switch before servicing.

Tools: ohmmeter

1. Open the cabinet door, disconnect the J1/P1 connector and remove the S3 harness connections.
2. Check with an ohmmeter that the switch contacts close according to the contact connect chart for each switch position.
3. Also check for good connections between the switch terminals and the harness.

Tools: Digital ohmmeter

1. Remove the brush block assembly to access the slip rings.
2. For grounded winding: on the highest resistance scale, touch one probe to the rotor shaft and the other to either slip ring.
3. Replace the rotor assembly if the meter does not indicate an open circuit to ground.
4. For winding resistance: select the best scale to measure a 20 to 25 ohm value and touch the probes to the slip rings.
5. Resolder slip ring to rotor lead connections if resistance is high; replace the rotor if windings do not meet specification.