Onan HGJAA-HGJAF error code 12 (Overvoltage)
Controller unable to maintain rated voltage. Instantaneous: AC S1-S2 >150 VAC. Delayed: 138-150 VAC for 3 continuous minutes.
What to check, and in what order, is in the app. The flow Onan Code 12 — Overvoltage 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)
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