Onan Generator: “Fault 3”
warning RV generator fault codes
What it means
First-level 'service check' fault. Three blinks tell you the controller has logged a problem and is holding a more specific two-digit code underneath. Code 3 itself is not the diagnosis; it is the prompt to read out the detailed second-level fault number.
Most likely causes
- Any logged second-level fault condition (the controller flashes 3 to signal one exists) most likely
Safe checks you can do yourself
- Press the Stop button on the generator control switch once to make the hidden two-digit fault code blink out (tens digit, brief pause, units digit).
- Count the blinks carefully and write the two-digit number down, then look that number up.
- Note: Code 3 and Code 4 are genuine single-digit first-level faults — do not mistake them for second-level codes 33 or 44, which Onan never assigned.
How to reset / clear Fault 3
- After reading the underlying two-digit code, address that specific fault.
- Press Stop to stop the blinking; the controller clears the indication once the start sequence succeeds again.
When to call a technician
If you cannot read out or interpret the second-level code, or the underlying code calls for a dealer.
Applies to
Marquis Gold · QG 4000 · QG 5500 · KY series · HGJAA · HGJAB · HGJAC · HGJAD · HGJAE · HGJAF
FAQ
What does Onan Generator code "Fault 3" mean?
First-level 'service check' fault. Three blinks tell you the controller has logged a problem and is holding a more specific two-digit code underneath. Code 3 itself is not the diagnosis; it is the prompt to read out the detailed second-level fault number.
How do I reset Onan Generator Fault 3?
After reading the underlying two-digit code, address that specific fault. Press Stop to stop the blinking; the controller clears the indication once the start sequence succeeds again.
What is the most common cause of Fault 3 on a Onan Generator?
The most likely cause is any logged second-level fault condition (the controller flashes 3 to signal one exists).
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Sources
- Onan Troubleshooting Codes (Service Manual Table 5) — Table 5, Troubleshooting — Service Check Fault Code No. 3 (Cummins Onan (hosted by Heartland Owners))
- RV Generator Handbook (Cummins Onan) — Fault Codes — blink-code readout procedure (Cummins Power Generation)
Note: Blink-readout procedure applies to the deluxe/electronic control. Some basic control switches differ slightly. Always confirm against the manual for your exact spec code.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.