Cummins Onan · HGLAA and compatible controllers; verify model applicability

Code 15Output under frequency

Generator output frequency fell below its protection limit and the controller shut the set down.

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

What it means

Plain-English answer

The set could not maintain output frequency within its protection range. An excessive load may contribute, but internal fuel, engine, speed-control, or electrical faults require model-specific diagnosis.

Owner-safe checks

What to check first

01
Turn off all generator-fed appliances and breakers before another start attempt.
02
Confirm adequate fuel and unobstructed cooling-air openings.
03
Record whether the fault appears with no load or only after a specific appliance starts.

Safety boundary

Stop and call a technician when

The fault returns with all RV loads disconnected.
The engine surges, smokes, overheats, or sounds mechanically abnormal.

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