What is it if a heat pump stays on heat but calling for cool?

If your heat pump continues blowing heat while your thermostat is actively calling for cool air, it points to a serious control communication or mechanical failure within the system. The most common cause is a stuck reversing valve, which is the internal component responsible for shifting refrigerant flow between heating and cooling modes; if the valve sticks mechanically or fails to receive electrical switching signals from the thermostat, the system stays locked in heating mode regardless of user settings. Another frequent issue is a miswired thermostat control cable where the O/B reversing valve wire is crossed, disconnected, or shorted out. You can verify this fault by checking if the outdoor compressor runs while indoor air remains heated. Professional HVAC technician service is required to test voltages and replace stuck reversing valves.