Keystone air conditioner displays E8 and may shut down or not start, often related to overheat or overload.

Safety: Unplug the unit. The compressor and condenser area can be very hot immediately after operation; allow it to cool.

Steps:

• Improve airflow: Ensure the rear of the unit (outdoor side) has at least the clearance specified in the manual and is not blocked by walls, curtains, or debris.
• Clean condenser coil: Remove the outer case and gently brush or vacuum dust and lint from the condenser fins. Straighten bent fins with a fin comb.
• Check fan operation: Confirm the outdoor/condenser fan runs at full speed when the compressor is on. If it is slow or not running, test and replace the fan motor or capacitor as needed.
• Inspect overload and sensors: Locate the compressor overload protector and any high-temp sensors on the discharge line. Check for loose connections or signs of overheating.
• Reset and test: After cleaning and inspection, reassemble, plug in, and run the unit. If E8 returns quickly under normal conditions, the high-temp sensor or main control board may be faulty and require replacement.