Keystone air conditioner displays H2 and may limit compressor operation.

Steps:

• Check installation: Ensure the rear of the unit has adequate clearance and is not installed in an enclosed space.
• Clean condenser: Remove dust and debris from the outdoor coil fins.
• Verify fan operation: Confirm the outdoor fan runs whenever the compressor is on. Replace the fan motor or capacitor if it is slow or not starting.
• Reduce load: Close windows and doors, use curtains to block direct sun, and avoid extreme setpoints in very hot weather.