Indoor unit runs but does not heat effectively in heating mode; air is lukewarm and room stays cold

Safety first: Turn off power before touching the outdoor unit. Ice can fall and cause injury.

• Inspect outdoor coil: During heating, check if the outdoor coil is heavily iced. Some frost is normal, but a solid block of ice is not.
• Clear obstructions: Remove snow, leaves, or covers blocking the outdoor unit. Maintain adequate clearance around it.
• Allow defrost cycles: The unit will periodically defrost; do not interrupt power during defrost. Observe if steam is released and ice melts.
• Clean outdoor coil: When weather permits and coil is ice-free, clean the coil with low-pressure water.
• Technician evaluation: If heating remains weak, a technician should check refrigerant charge, defrost control operation, and confirm the unit is suitable for the local minimum outdoor temperature.