Heat Pump Stuck In Defrost Mode. If you think your heat pump is not going into defrost mode, have a professional thoroughly inspect your unit to find out the exact issue. Plus, the unit takes in outside air to run.
For the defrost mode to go back to normal heating mode. As we’ve seen, the load size is a critical factor in defrost cycling. If the valve is stuck, your heat pump won’t be able to switch to heating mode (or cooling during the defrost mode).