Cummins/Onan LRG-423 Engine

How to read your Cummins/Onan engine serial & model number →

• The OVERLOAD lamp lights. Engine shuts down.
  Cause: If load exceeds generator current rating, the breaker will trip preventing the generator from being overloaded.
  Fix: Locate the source of overload and correct as necessary. Manually reset breaker to reconnect the load to the generator.
• The O/U VOLTAGE lamp lights. Engine shuts down.
  Fix: Contact an authorized service center for service.
• SWITCH OFF lamp flashes.
  Fix: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used. Move the Run/Stop/Remote switch to the Remote position for automatic starting.
• Pre-Low Oil Pressure
  Fix: A pre-low oil pressure sensor and lamp provides an alarm that oil pressure is marginally low, 20 psi (137 kPA) or less. The cause should be found and corrected as soon as possible.
• Pre-High Engine Temperature
  Fix: A pre-high engine temperature sensor and lamp provides an alarm that engine temperature is marginally high, 215° F (102° C). The cause should be found and corrected as soon as possible.
• PRE HET/LOP lamp lights. Engine continues to operate.
  Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 205°F (97°C) or coolant level is low.
  Fix: A. Reduce load if possible by turning off non-critical loads. b. Check air inlets and outlets and remove any obstructions to airflow.
• OVERCRANK lamp lights and engine stops cranking.
  Cause: Indicates possible fuel system problem.
  Fix: A. Check for empty fuel tank (LPG Vapor), fuel leaks, or plugged fuel lines and correct as required. b. Check for dirty fuel filter and replace if necessary (see Maintenance section). c. Check for dirty or plugged air filter and replace if necessary (see Maintenance section). d. Reset the control and restart after correcting the problem. Contact an authorized service center for service if none of the above.
• No AC output voltage.
  Fix: Field breaker is tripped. Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.
• Low Oil Pressure
  Fix: Shuts down the engine immediately if oil pressure drops below 14 psi (97 KPA) and lights a fault lamp. The fault is time-delayed about 10 seconds following starter disconnect and inhibited during cranking.
• Low Coolant Level Shutdown
  Fix: An electronic switch that provides engine shutdown and turns on the high engine temperature fault lamp if coolant level fails too low.
• LO OIL PRES lamp lights. Engine shuts down.
  Cause: Indicates engine oil pressure has dropped to 30 psi (207 kPa).
  Fix: NOTE: See also step 5.
• LO FUEL (Pressure) lamp lights. Shutdown will occur if unit runs out of fuel. LO FUEL (Pressure)
  Fix: Install the fuel hose and regulator supplied with the unit and connect to a propane fu
• Hl ENG TEMP lamp lights. Engine shuts down. Hl ENG TEMP
  Cause: Engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low.
  Fix: A. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check for a slipping fan belt and tighten if loose. d. Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above.
• High Engine Temperature
  Fix: Shuts down the engine immediately if coolant temperature rises above 222° F (106° C) and lights a fault lamp. The fault is time-delayed about 10 seconds following starter disconnect and inhibited during cranking.
• HI ENG TEMP lamp lights. Engine shuts down.
  Cause: Indicates engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low.
  Fix: A. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check for a slipping fan belt and tighten if loose. d. Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan LRG-423.

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.