Onan HGJAA-HGJAF (HGJAD/E/F) error code 31 (Overspeed)
Overspeed (per source manual ch.12.25, only triggered in ERO/Engine Run Only mode): 5 kW sets >2880 RPM via ignition pulse; 7 kW sets >3360 RPM via ignition pulse.
What to check, and in what order, is in the app. The flow Onan Code 31 — Overspeed (>2880 RPM 5 kW / >3360 RPM 7 kW, ERO mode) walks this code step by step with the pass/fail measurements, wiring schematics and procedures that go with it, and it works offline in the bay.
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- Cummins-Onan Service Manual (document 0983-0501 Issue 26, March 2018, 202 pp) covering HGJAA Spec A-E / HGJAB A-E / HGJAC A-C / HGJAD A-E / HGJAE A-E / HGJAF A-C (rv-tech-resources/25-onan-hgjaa/0983-0501_Onan_HGJAA-HGJAF_Service_Manual_Issue_26.pdf)
- Onan HGJAA Generator Technician Service Diagnostic Reference (rv-tech-resources/25-onan-hgjaa/Onan_HGJAA_Generator_Technician_Service_Diagnostic_Reference.md)