Cummins Onan · HGLAA and compatible controllers; verify model applicability

Code 12Output over voltage

Generator output voltage rose above the controller's protection limit and the set shut down.

Published by RV Fault Finder · Independent referencePrimary source checked August 2026How this guide is researched →

What it means

Plain-English answer

The generator detected output voltage above its safe range. The manufacturer directs this fault to qualified service because diagnosis involves regulated generator output and internal components.

Owner-safe checks

What to check first

01
Turn off generator-fed breakers and appliances.
02
Record the model, specification letter, and complete blink sequence.
03
Leave the generator off until its output can be tested by qualified service.

Safety boundary

Stop and call a technician when

Do not reconnect sensitive appliances to test the output.
Do not adjust internal voltage or inverter components.

Primary reference

Check the exact manual

Applicability: HGLAA and compatible controllers; verify model applicability. The data plate and specification letter determine which procedure is correct.

Open Cummins Onan HGLAA operator manual ↗Source reviewed August 2026