Service Fault: Read the Two-Digit Code (3 Blinks)
The ONAN-3 (Cummins Onan) diesel fault code means: Service Fault: Read the Two-Digit Code (3 Blinks). This is a moderate severity code.
- DIY difficulty
- moderate
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What Are the Symptoms of ONAN-3?
- The generator shut down and the status light blinks three times, pauses, and repeats
What Causes ONAN-3? (Most Likely First)
- Three blinks is not a fault by itself: Cummins defines it as a service fault with a second-level, two-digit code behind it Very Likely
Frequently Asked Questions
Does three blinks mean overspeed?
No. Cummins defines three blinks as a service fault: press Stop once to see the two-digit code that explains the shutdown.
Where do I find what the two-digit code means?
Cummins' handbook refers owners to the operator's manual for the complete list.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose ONAN-3?
Press Stop once. The status light starts blinking the two-digit code: the first group of blinks is the tens digit and the second group the units digit. Code 36, for example, is three blinks, a pause, then six blinks.
Pressing Stop again stops the blinking.
Look up the two-digit code in your generator's operator's manual. Code 36 is the most common one (see ONAN-36).
Do not read three blinks followed by four blinks as anything other than the two-digit code being shown: Cummins notes that 33 and 44 are not assigned as fault codes, so do not mistake first-level codes 3 and 4 for them.
The code stops blinking after five minutes (15 minutes on Series HGJAA). To see it again, press Stop three times within five seconds; the last logged fault blinks even if the condition has cleared.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
Which Vehicles Commonly Get ONAN-3?
- Cummins Onan RV generators with a status light on the Start/Stop switch (gasoline, LP and diesel models)
- Not the RV QD 3200, which shows text messages on its display panel
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