I have an electric heat pump and when you turn the thermostat on to heat, the aux heat comes on immediately and the air handler will not shut off even after the set temperature is reached. It just keeps blowing hot air with the aux heat on. The heat pump cycles like it should but the air handler will not. When the thermostat is on cool, everything works fine. The air comes off and on like it should. Should I suspect a sequencer on the heat circuit?