How Do I Properly Maintain And Operate A Generator’s DEF System?

Proper DEF system maintenance is essential for reliable generator performance. The way DEF is stored and how the unit is operated directly affects system health. DEF should always be kept out of direct sunlight and stored in a temperature-controlled environment below 86°F. Heat and sunlight degrade DEF, while cold temperatures do not cause damage. A shaded indoor area around 50°F is ideal for long-term storage. The DEF header inside the tank is sensitive and relies on accurate temperature, level, and quality readings, so proper storage helps protect these components.

During generator operation, the engine should always be allowed to warm up before load is applied and cool down before shutdown. This supports proper oil circulation, protects the turbocharger, and allows the DEF system to purge unused fluid from the injection lines. If the system cannot complete this purge cycle, leftover DEF can overheat, crystallize, and block the line. This often triggers “SCR Malfunction” or “Broken Device” codes that prevent normal operation and may require software clearing or component cleaning and replacement.

DEF quality is also critical. Only purchase DEF from reputable suppliers that use automotive-grade urea and proper deionized water. Poor manufacturing or contamination can quickly damage components in the DEF system.

When refilling the DEF tank, allow the level to drop naturally before refilling. Frequent “topping off” prevents the DEF header from detecting normal level changes and can cause false codes. DEF tanks are sized to last for two full fuel tank cycles. Avoid filling DEF while the generator is running, since air bubbles can interfere with the level sensor.

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