If an air conditioner (AC) stops blowing cold air after sitting unused for about three hours but works fine otherwise, there are a few potential reasons for this issue:
Low Refrigerant Levels: One of the most common reasons for the AC not blowing cold air is low refrigerant levels. Refrigerant is the substance responsible for cooling the air in the AC system. If there's a leak in the system, the refrigerant can gradually escape, leading to decreased cooling capacity. When the AC is left unused for a few hours, the pressure in the system might drop, exacerbating the issue.
Thermostat Settings: It's possible that the thermostat settings are not adjusted correctly. If the thermostat is set to "fan only" mode or a higher temperature setting, the AC might not engage the cooling function, resulting in warm air blowing from the vents.
Frozen Evaporator Coil: The evaporator coil inside the AC can freeze up due to various reasons, such as restricted airflow, dirty filters, or a malfunctioning blower motor. When the coil freezes, it blocks the air circulation, resulting in the AC blowing warm air.
Electrical Issues: There could be electrical problems in the AC system, such as a faulty capacitor, relay, or compressor clutch. These issues may cause intermittent cooling performance, and the problem might become more noticeable after the unit has been inactive for a few hours.
Dirty Air Filters: Dirty or clogged air filters can hinder proper airflow through the AC system. Reduced airflow can lead to the evaporator coil getting too cold and freezing up, leading to warm air being blown instead of cool air.
Sensor Issues: Some AC units have sensors that monitor various conditions, such as temperature or pressure. If these sensors are malfunctioning, they may not provide accurate information to the AC system, affecting its cooling performance.
To address the issue, consider the following steps:
Check the thermostat settings and ensure the AC is set to the cooling mode at the desired temperature.
Inspect the air filters and replace them if they are dirty or clogged.
If the issue persists, it's best to have a professional HVAC technician inspect the AC system. They can check for refrigerant leaks, test electrical components, clean the evaporator coil, and address any other potential problems.
Regular maintenance of the AC system is essential to ensure its optimal performance. It's recommended to schedule periodic inspections and servicing to prevent issues and maintain the efficiency of the air conditioning system.