Onan Generator: “Fault 3”
warning RV generator fault codes
What it means
Service check — a first-level fault shown as three blinks. Three blinks is not the fault itself: it tells you the controller has stored a two-digit second-level code. Press Stop once and the light blinks the tens digit, pauses, then the units digit.
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.
Accuracy notes
Do not read three blinks as code 33. Cummins left 33 and 44 unassigned on purpose so that the first-level three and four blinks can never be confused with a second-level code. If pressing Stop produces nothing, the display may simply have timed out — press Stop three times within five seconds to bring it back.
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?
Service check — a first-level fault shown as three blinks. Three blinks is not the fault itself: it tells you the controller has stored a two-digit second-level code. Press Stop once and the light blinks the tens digit, pauses, then the units digit.
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).
Related · Onan generator
Overcrank — a first-level fault shown as four blinks. The starter turned… Fault 36
Engine Stopped fault. The engine stopped on its own without the… Fault 32
Low cranking speed fault. During start the engine cranked slower than… Fault 13
Undervoltage fault. The controller could not hold the generator's AC…
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)
- Operator Manual — RV Generator Set KY (Spec J–N) — 981-0159 (Issue 9), Section 4 Troubleshooting, Table 2 (Cummins Inc. (Onan))
- Cummins Onan RV Generator Handbook (2019 edition) — Fault Codes, p. 38 (Cummins Inc. (hosted by Forest River))
● Checked against 4 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