Generator fails to start; E03 is displayed after cranking stops.

Safety first: Ensure the generator is in OFF mode and the ATS is isolated. Wear eye protection when working around batteries.

• Visual inspection: Check the Hyundai standby generator battery for swelling, cracks, or leakage. Inspect terminals for corrosion (white/green deposits).
• Clean and tighten terminals: Disconnect the negative terminal first, then the positive. Clean posts and clamps with a wire brush and a baking soda solution if corroded. Reinstall clamps (positive first, then negative) and tighten securely.
• Measure battery voltage: Use a multimeter. A healthy 12 V battery should read about 12.6 V at rest. If below ~12.0 V, recharge with an appropriate charger or replace it.
• Check onboard battery charger: With AC utility present and the generator in standby, measure the voltage at the battery. It should be around 13.2–13.8 V. If not, inspect the Hyundai battery charger module, its fuse, and wiring. Replace the charger if it is not outputting correctly.
• Retest start: Clear E03 on the controller and attempt a manual start. If the battery quickly drops under load or E03 returns, replace the starting battery with a Hyundai-approved capacity and type.