Keystone portable air conditioner shows E9 and stops operating, often associated with water level or pump issues.

Safety: Turn off and unplug the unit. Water and electricity are a dangerous combination; keep the area dry while working.

Steps:

• Drain water: Use the lower drain port to remove all water from the internal tank. Tilt the unit slightly if needed to fully drain.
• Access pump assembly: Remove the rear or side panel (per manual) to locate the small condensate pump and its reservoir.
• Clean reservoir and float: Remove any slime, algae, or debris from the pump basin. Ensure the float moves freely up and down.
• Check discharge line: Verify the pump outlet hose is not kinked, blocked, or routed uphill excessively.
• Test pump (advanced): With the unit unplugged, disconnect the pump and check coil resistance. If open, replace the pump. If you can safely power the pump separately, verify it runs and discharges water.
• Replace components: Install a new condensate pump or float switch assembly if defective. Reassemble and test for leaks and proper operation.