Goodman communicating thermostat shows d4 and system may not reach setpoint

Safety first: Turn off power before cleaning coils or opening panels.

Steps to improve performance:

• 1. Replace filters: Ensure Goodman air handler or furnace filters are clean.
• 2. Clean indoor and outdoor coils: Have the evaporator coil professionally cleaned if dirty; rinse the condenser coil yourself if accessible.
• 3. Reduce heat load: Close blinds during peak sun, seal obvious air leaks, and avoid using heat-generating appliances during the hottest part of the day.

When to call a professional: If d4 persists under normal conditions, a technician should check system sizing, ductwork, and refrigerant charge.