Unit stops with H28; often related to frost or defrost control issues.

Safety first: Turn off power before servicing.

Steps:

• 1. Check air filters: Remove and clean filters thoroughly with water and mild detergent. Dry completely before reinstalling.
• 2. Inspect indoor fan operation: In fan-only mode, ensure the blower runs smoothly. If not, address fan motor issues.
• 3. Inspect coil sensor: Confirm the indoor coil thermistor is properly clipped to the coil and wiring is intact.
• 4. Defrost the coil: If the coil is iced over, leave the unit off and open the front panel to allow ice to melt naturally. Do not use sharp tools.

If H28 recurs after airflow and sensor checks, the thermistor or indoor PCB may need replacement.