Controller shows AIR FILTER or MAINTENANCE AIR FILTER; generator may run rich or lack power.

Safety first: Turn the controller to OFF and open the main breaker. Allow the engine to stop completely.

• Inspect air filter: Remove the air filter cover and take out the element. If it is dark, oily, or packed with dust, replace it with a Guardian-specified filter.
• Clean housing and intake: Wipe out the air box and remove leaves or debris from the intake louvers.
• Reset maintenance reminder: Use the controller menu to reset the air filter or maintenance interval per the Guardian manual.
• Test run: Start the generator and verify smooth operation and normal power output.