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.
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).
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Sources
- Onan Troubleshooting Codes (Service Manual Table 5) — Overcurrent (Field Overload) Fault — Code No. 38 (Cummins Onan (hosted by Heartland Owners))
Note: Codes 35 (control card EEPROM error), 37 (invalid genset configuration / wrong frequency-rpm ratio) and 45 (speed sense / quadrature frequency) are also confirmed in the same manual but are all dealer-only faults; omitted here in favor of owner-actionable codes within the 8-record limit.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.