GMC Acadia front heater vents blowing cold air unless set to HI with no fault codes detected on GMC Acadia

Some GMC Acadia owners report experiencing issues with front heater vents blowing cold air unless set to the highest setting, despite no fault codes being detected. This problem may be attributed to several underlying issues, including low coolant levels or air in the cooling system, a clogged heater core, or a malfunctioning thermostat. Additionally, some owners may find that a faulty blend door actuator, bad water pump, dirty cabin air filter, or a malfunctioning blower motor could be contributing factors. In cases where the heater vents do not respond to temperature adjustments, it is recommended that owners seek a professional mechanic's inspection to accurately diagnose and resolve the issue.