Onan Generator: “Fault 38”
warning RV generator fault codes
What it means
Overcurrent (field overload) fault. The generator saw excessive current from low-power-factor loads — commonly motor-starting surges, especially from air conditioners.
Most likely causes
- Too many high-surge appliances starting at once (multiple A/C units) most likely
- A faulty appliance with very low power factor, e.g. an air conditioner with a locked compressor rotor common
Safe checks you can do yourself
- Reduce how many appliances run simultaneously, especially those with high motor-starting loads like air conditioners.
- Have air conditioners and other suspect appliances checked for proper operation — a seized/locked compressor can cause a very low power factor and trip this fault.
- Stagger startup of large loads instead of switching them all on together.
How to reset / clear Fault 38
- Shed or stagger loads, then restart the generator from the control switch.
- If it runs cleanly with loads managed, the appliance load was the cause.
When to call a technician
If Code 38 recurs with normal, well-managed loads, or if a specific appliance is suspected of a locked-rotor fault.
Accuracy notes
The air-cooled manuals describe this only as 'low power factor loads'. The Quiet Diesel manual gives the measurable version: field voltage above 180 VAC for ten seconds. The lower the power factor of a motor or compressor, the more current it draws per kilowatt, and the harder the controller has to push the field to keep up — which is why a locked air conditioner compressor rotor triggers this so reliably.
Applies to
Marquis Gold · QG 4000 · QG 5500 · KY series · HGJAA · HGJAB · HGJAC · HGJAD · HGJAE · HGJAF
FAQ
What does Onan Generator code "Fault 38" mean?
Overcurrent (field overload) fault. The generator saw excessive current from low-power-factor loads — commonly motor-starting surges, especially from air conditioners.
How do I reset Onan Generator Fault 38?
Shed or stagger loads, then restart the generator from the control switch. If it runs cleanly with loads managed, the appliance load was the cause.
What is the most common cause of Fault 38 on a Onan Generator?
The most likely cause is too many high-surge appliances starting at once (multiple a/c units).
Related · Onan generator
Governor actuator overload. The controller had to hold the governor… Fault 13
Undervoltage fault. The controller could not hold the generator's AC… Fault 15
Underfrequency fault. The engine governor could not keep the engine…
Sources
- Onan Troubleshooting Codes (Service Manual Table 5) — Overcurrent (Field Overload) Fault — Code No. 38 (Cummins Onan (hosted by Heartland Owners))
- Operator Manual — RV Generator Set KY (Spec J–N) — 981-0159 (Issue 9), Section 4 Troubleshooting, Table 2 (Cummins Inc. (Onan))
- Operator Manual — RV Generator Set HDKCA / HDKCB (Spec A–E) — 0981-0173 (Issue 10), Section 4 Troubleshooting, Table 4-1 (Cummins Inc. (Onan Quiet Diesel))
● Checked against 3 manufacturer documents · Last verified 2026-08-07 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual. How we verify