The A1 is a generator-set controller. It is used on generator sets from Cummins/Onan, including the 3.6MKY, 4MKY, 5.5 HGJAA and 5.5 HGJAB.
Also fitted to: Cummins/Onan HDKBA / HDKBB / HDKBC, Cummins/Onan HGJAA/HGJAB/HGJAC (5.5 LPG), Cummins/Onan HGJAA/HGJAB/HGJAC (6.5 LPG), Cummins/Onan MDKAU.
| Code | Meaning | Remedy |
|---|---|---|
| 1 | HIGH ENGINE TEMPERATURE | 1. Add coolant as necessary and repair leaks (Page 18). 2. Replace the engine thermostat, which might not be opening fully (Page 21). 3. Clean the raw water tubes in the heat exchanger, which might be clogged with scale (Page 22). 4. Flush the coolant system to remove coolant passage fouling (Page 18). |
| 1 | HIGH ENGINE TEMPERATURE—CODE NO. 1 (Engine coolant temperature exceed design limit) | 1. Check for and clean a blocked sea water strainer. If above the water line, fill the strainer with water to assist priming. 2. Check engine coolant level and add coolant as necessary. 3. Check for kinked or leaking hoses and reconnect, reroute or replace. 4. Check the V-belt that drives the coolant pump and service as necessary 5. Inspect the siphon break (if provided) for proper operation. 6. Check for a worn raw water impeller and replace as necessary 7. Clean the heat exchanger |
| 1 | HIGH ENGINE TEMPERATURE—CODE NO. 1 (Engine coolant temperature exceeds design limit) | 1. Check for and clean a blocked sea water strainer. If above the water line, fill the strainer with water to assist priming. 2. Check engine coolant level and add coolant as necessary. 3. Check for kinked or leaking hoses and reconnect, reroute or replace. 4. Check the V-belt that drives the coolant pump and service as necessary (p. 4-13). 5. Inspect the siphon break for proper operation (p. 4-8). 6. Check for a worn raw water impeller and replace as necessary (p. 4-12). 7. Clean the heat exchanger (p. 4-8). 8. Check the bottom of the hull for any blockage at the through-hull fitting. 9. Replace the coolant thermostat, which might not be opening fully (p. 4-14). 10. Drain and clean the coolant system to remove coolant passage fouling (Page 4-7). |
| 1 or 2 digit code | Status light on the generator will repeatedly blink a 1 or 2 digit code after a protective shutdown | |
| 12 | HIGH AC VOLTAGE—CODE NO. 12 (After voltage regulation was enabled Output Voltage jumped to more than 125% of rated for 75 milliseconds or to more than 115% of rated for 3 seconds) | 1. Check for a tripped generator set circuit breaker, reset if necessary, and run with fewer loads. (A breaker tripping under load can cause generator set voltage to overshoot.) 2. Check all fuel fittings and filters for fuel and air leaks and tighten as necessary. (Air bubbles can disrupt generator set frequency/voltage.) 3. Prime the engine fuel system for at least 30 seconds (p. 3-3). |
| 12 | OVERVOLTAGE | See an authorized Onan dealer. |
| 12 | OVERVOLTAGE FAULT—CODE NO. 12 | See an authorized Onan dealer. |
| 12 | Overvoltage | |
| 13 | LOW AC VOLTAGE—CODE NO. 13 (After voltage regulation was enabled Output Voltage fell to less than 90% of rated for 5 seconds) | 1. Push the generator set line circuit breaker OFF and disconnect the PTO, if so equipped. If the generator set now runs and voltage and frequency are normal, reduce the number of electrical and mechanical (PTO) loads. 2. Check the fuel tank and fill as necessary. (Note: The arrangement of pickup tubes in the fuel supply tank probably is such that the generator set will run out of fuel before the propulsion engines.) 3. Check all fuel fittings and filters for fuel and air leaks and tighten as necessary. (Air bubbles can disrupt generator set frequency/voltage.) 4. Replace fuel filters (p. 4-6). |
| 13 | UNDERVOLTAGE | Reduce the number of connected appliances, especially when air conditioners and battery chargers are running. |
| 13 | UNDERVOLTAGE FAULT—CODE NO. 13 | Reduce the number of connected appliances, especially when air conditioners and battery chargers are running. |
| 13 | Undervoltage | |
| 14 | HIGH AC FREQUENCY—CODE NO. 14 (After the starter was engaged Frequency jumped to more than 70 Hz for 40 milliseconds or to more than 2% over nominal for 6 seconds) | 1. Check for a tripped genset circuit breaker, reset it if necessary, and run with fewer connected loads. 2. Check all fuel fittings for fuel and air leaks and tighten as necessary and reprime. |
| 14 | OVERFREQUENCY | 1. If the line circuit breaker or any other circuit breaker has tripped, start the genset before resetting the breaker. (Frequency can overshoot when a circuit breaker trips under load.) If the genset continues to run, turn off or disconnect all loads, reset the breaker and bring the loads on one at a time without overloading the genset. 2. Tighten loose fuel line fittings so that air cannot be drawn in by genset lift pump suction. 3. Prime the fuel system to remove air in the fuel lines (Page 8). |
| 14 | OVERFREQUENCY FAULT—CODE NO. 14 | See an authorized Onan dealer. |
| 14 | Overfrequency | Check engine speed, loads, governor actuator operation, fuel supply, control plugs fully seated, quad leads fully seated in connector to control, quad winding resistance |
| 15 | LOW AC FREQUENCY—CODE NO. 15 (During normal operation Frequency fell to less than 90% of nominal for more than 8 seconds) | Push the genset line circuit breaker OFF. If the genset now runs, reduce the number of loads. |
| 15 | UNDERFREQUENCY FAULT—CODE NO. 15 | Reduce the number of connected appliances, especially when air conditioners and battery chargers are running. |
| 15 | UNDERFREQUENCY—CODE NO. 15 (Engine governor unable to maintain rated frequency) | 1. Reduce the number of appliances running at the same time, especially those with high motor starting loads such as air conditioners. 2. Check the fuel tank and fill as necessary. (Note: The arrangement of pickup tubes in the fuel supply tank probably is such that the genset will run out of fuel before the propulsion engines.) 3. Remove any blockage in the combustion air inlet (lower rear of left end of genset). 4. Tighten loose fuel line fittings so that air cannot be drawn in by genset lift pump suction. 5. Drain the fuel filter of water and sediment (Page 15) and prime the fuel system (Page 8). 6. Drain and/or replace fuel supply system filters and prime the fuel system (Page 8). |
| 15 | Underfrequency | Check engine speed, loads, governor actuator operation, fuel supply, control plugs fully seated, quad leads fully seated in connector to control, quad winding resistance |
| 17 | Fuel Pump Fault | |
| 17 | OVER-PRIME—CODE NO. 17 (Prime mode exceed 5 minutes) | Check for and remove any object that may be holding either control switch (remote or local) in the prime position. |
| 17 | Overprime | Check battery voltage, fuel supply, start/stop switch (local and remote), shorted wiring |
| 19 | GOVERNOR ACTUATOR—CODE NO. 19 (Controller sensed an open or short circuit in actuator circuit) | See an authorized Onan dealer. |
| 19 | Governor Actuator (EFI Only) | |
| 2 | LOW OIL PRESSURE | Add engine oil or drain excess oil, as necessary (Page 14). |
| 2 | LOW OIL PRESSURE SHUTDOWN—CODE NO. 2 | 1. Check engine oil level and add oil as necessary (Page 17). 2. Drain excess oil (above dipstick Full mark.) |
| 2 | LOW OIL PRESSURE—CODE NO. 2 (Low oil pressure) | Check the engine oil level and add or drain oil as necessary (p. 4-3). Repair any oil leaks. |
| 2 | Low Oil Pressure Fault | |
| 2 | Status indicator light on the Control Switch blinks 2 times. | |
| 22 | Actuator Overload | Check load, fuel supply, intake restriction, governor actuator operation; Perform checks in step 01; Check exhaust back pressure; Perform checks in step 02; Check field windings, proper field resistance reading, open to ground, brush condition and contact |
| 22 | GOVERNOR OVERLOAD—CODE NO. 22 (Maximum allowable time at full-duty cycle was exceeded) | 1. Reduce the number of appliances running at the same time, especially those with high motor starting loads such as air conditioners. 2. Check the fuel tank and fill as necessary. (Note: The arrangement of pickup tubes in the fuel supply tank probably is such that the genset will run out of fuel before the propulsion engines.) 3. Remove any blockage in the combustion air inlet (lower rear of left end of genset). 4. Tighten loose fuel line fittings so that air cannot be drawn in by genset lift pump suction. 5. Drain the fuel filter of water and sediment (Page 15) and prime the fuel system (Page 8). 6. Drain and/or replace fuel supply system filters and prime the fuel system (Page 8). |
| 22 | Governor Actuator Overload (EFI Only) | |
| 23 | FAULTY OIL PRESSURE SENDER—CODE NO. 23 (Controller sensed shorted or grounded sender) | See an authorized Onan dealer. |
| 23 | Faulty Oil Pressure Sender | Check oil level, grounded or shorted sender lead, sender resistance (low); Perform checks in step 01; Check oil pressure (mechanical) |
| 23 | Oil Pressure Switch Fault | |
| 24 | FAULTY TEMPERATURE SENDER—CODE NO. 24 (Controller sensed open or grounded sender) | See an authorized Onan dealer. |
| 24 | Faulty Temperature Sender | Check coolant level, open or loose sender lead, sender resistance (high); Perform checks in step 01; Check coolant temperature |
| 27 | LOSS OF VOLTAGE SENSE—CODE NO. 27 (Controller unable to sense output voltage) | See an authorized Onan dealer. |
| 27 | Loss of Voltage Sense | Check AC output, sense lead connections, control plugs fully seated, sense leads fully seated in connector to control, field windings, proper field resistance reading, open to ground, brush condition and contact, grounded or shorted main windings |
| 27 | VOLTAGE SENSE FAULT—CODE NO. 27 | See an authorized Onan dealer. |
| 27 | Voltage Sense Lost | |
| 29 | HIGH BATTERY VOLTAGE FAULT—CODE NO. 29 | 1. Check battery bank connections and reconnect if necessary so that the 12 volt batteries serving the genset are connected in parallel (12 v |
| 29 | HIGH BATTERY VOLTAGE—CODE NO. 29 (Battery system at more than 19.2 volts) | 1. Check battery bank connections and reconnect if necessary to supply 12 volts. 2. Select a lower battery boost charge rate. |
| 29 | High Battery Voltage | Check battery voltage, battery connections, battery charge rate |
| 3 | SERVICE CHECK | Check the second-level shutdown code by pressing STOP once. The second-level shutdown code will have two-digits. The shutdowns are listed below in numerical order. |
| 3 | SERVICE CHECK FAULT—CODE NO. 3 | Check the second-level fault code by pressing STOP once. The second-level fault code will have two-digits. The faults are listed in numerical order in this table. |
| 3 | SERVICE CHECK SHUTDOWN—CODE NO. 3 | Check the second-level shutdown code by pressing STOP once. The second-level shutdown code will have two-digits. The faults are listed in numerical order in this table. |
| 3 | SERVICE CHECK—CODE NO. 3 (A fault with a 2-Digit Fault Code Number occurred) | Check the 2-Digit fault code by Pushing and Releasing Stop. The 2-Digit fault will be one of the following in this table. (Does not apply to Digital Display.) |
| 3 | Service Check Fault | |
| 3 | Service fault | Press Stop once to cause the two-digit shutdown code to blink |
| 3 | Status indicator light on the Control Switch blinks 3 times. | |
| 31 | Overspeed Fault | |
| 31 | Overspeed Fault (HGJAD, E, F Models Only) | |
| 32 | Low Cranking Speed Sense | |
| 33 | Fault Code 3 - Fault Code 33 | |
| 33 | Fault Code 33 | |
| 35 | CONTROL CARD FAILURE—CODE NO. 35 (Microprocessor EEPROM error during self-test) | See an authorized Onan dealer. |
| 35 | Control Card EE Checksum | Check verify fault |
| 35 | Control Card Failure |
Fault codes and symptom→remedy steps extracted from this controller’s service/owner documentation; verify against the official manual before servicing. Aggregated from the service documentation of generator sets built on this controller.