Controller shows AL20 – Air Filter Restriction (if differential pressure switch fitted)

Safety first: Stop the generator and ensure it cannot start automatically. Allow the engine to cool.

• Inspect air filter: Open the air filter housing and remove the primary element. If heavily soiled or oily, replace with a genuine FG Wilson/engine manufacturer element.
• Check intake ducting: Inspect the rubber intake hose between filter and turbocharger/manifold for collapse or internal obstruction.
• Clean intake grilles: Remove debris, dust, or plastic bags from the enclosure air intake louvers.
• Check restriction switch: If the filter is clean but alarm persists, inspect the differential pressure switch or vacuum indicator on the housing. Replace if stuck or faulty.
• Test run: After reassembly, clear the alarm and run the generator, confirming that engine power is normal and no restriction alarm appears.